Catalytic processes for preparing estolide base oils

ABSTRACT

Provided herein are processes for preparing estolides and estolide base oils from fatty acid reactants utilizing catalysts. Further provided herein are processes for preparing carboxylic esters from at least one carboxylic acid reactant and at least one olefin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 61/378,891, filed Aug. 31, 2010, andU.S. Provisional Patent Application No. 61/498,499, filed Jun. 17, 2011,both of which are incorporated herein by reference in their entiretiesfor all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

The subject of this invention was made with support under U.S.Department of Agriculture—Agricultural Research Service CooperativeResearch and Development Agreement (CRADA) Nos. 58-3K95-1-1508-M and58-3K95-6-1147. Accordingly, the government may have certain rights inthis invention.

FIELD

The present disclosure relates to catalytic processes for producingestolide compounds and compositions. The estolides described herein maybe suitable for use as biodegradable base oil stocks and lubricants.

BACKGROUND

Synthetic esters such as polyol esters and adipates, low viscosity polyalpha olefins (PAO) such as PAO 2, and vegetable oils such as canola oiland oleates have been described for use industrially as biodegradablebase stocks to formulate lubricants. Such base stocks may be used in theproduction of lubricating oils for automotives, industrial lubricants,and lubricating greases. Finished lubricants typically comprise the baseoil and additives to help achieve the desired viscometric properties,low temperature behavior, oxidative stability, corrosion protection,demulsibility and water rejection, friction coefficients, lubricities,wear protection, air release, color and other properties. However, it isgenerally understood that biodegradability cannot be improved by usingcommon additives that are available in today's marketplace. Forenvironmental, economical, and regulatory reasons, it is of interest toproduce biodegradable lubricating oils, other biodegradable lubricants,and compositions including lubricating oils and/or lubricants, fromrenewable sources of biological origin.

Estolides present a potential source of biobased, biodegradable oilsthat may be useful as lubricants and base stocks. Several estolidesynthetic processes have been previously described, such as thehomopolymerization of castor oil fatty acids or 12-hydroxystearic acidunder thermal or acid catalyzed conditions, as well as the production ofestolides from unsaturated fatty acids using a high temperature andpressure condensation over clay catalysts. Processes for the enzymaticproduction of estolides from hydroxy fatty acids present in castor oilusing lipase have also been described.

In U.S. Pat. No. 6,018,063, Isbell et al. described estolide compoundsderived from oleic acids under acidic conditions and having propertiesfor use as lubricant base stocks, wherein the “capping” fatty acidcomprises oleic or stearic acid. In U.S. Pat. No. 6,316,649, Cermak etal. reported estolides derived from oleic acids and having cappingmaterials derived from C₆ to C₁₄ fatty acids.

SUMMARY

Described herein are catalytic processes for preparing estolide baseoils and a carboxylic acid.

In certain embodiments, the catalytic processes include a process ofproducing an estolide base oil comprising: providing at least one firstfatty acid reactant, at least one second fatty acid reactant, and aLewis acid catalyst; and oligomerizing the at least one first fatty acidreactant with the at least one second fatty acid reactant in thepresence of the Lewis acid catalyst to produce an estolide base oil.

In certain embodiments, the catalytic processes include a process ofproducing an estolide base oil comprising: providing at least one firstfatty acid reactant, at least one second fatty acid reactant, and anoligomerization catalyst; and continuously oligomerizing the at leastone first fatty acid reactant with the at least one second fatty acidreactant in the presence of the oligomerization catalyst to produce anestolide base oil.

In certain embodiments, the catalytic processes include a process ofproducing a carboxylic acid ester, comprising: providing at least onecarboxylic acid reactant, at least one olefin, and a Bismuth catalyst;and reacting the at least one carboxylic acid reactant with the at leastone olefin in the presence of the Bismuth catalyst to produce acarboxylic acid ester.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. schematically illustrates an exemplary process system withcontinuous stirred tank reactor and separation unit according to certainembodiments.

FIG. 2. schematically illustrates a column reactor useful for theprocesses for synthesis of estolides according to certain embodiments.

DETAILED DESCRIPTION

As used in the present specification, the following words, phrases andsymbols are generally intended to have the meanings as set forth below,except to the extent that the context in which they are used indicatesotherwise. The following abbreviations and terms have the indicatedmeanings throughout:

A dash (“-”) that is not between two letters or symbols is used toindicate a point of attachment for a substituent. For example, —C(O)NH₂is attached through the carbon atom.

“Alkoxy” by itself or as part of another substituent refers to a radical—OR³¹ where R³¹ is alkyl, cycloalkyl, cycloalkylalkyl, aryl, orarylalkyl, which can be substituted, as defined herein. In someembodiments, alkoxy groups have from 1 to 8 carbon atoms. In someembodiments, alkoxy groups have 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms.Examples of alkoxy groups include, but are not limited to, methoxy,ethoxy, propoxy, butoxy, cyclohexyloxy, and the like.

“Alkyl” by itself or as part of another substituent refers to asaturated or unsaturated, branched, or straight-chain monovalenthydrocarbon radical derived by the removal of one hydrogen atom from asingle carbon atom of a parent alkane, alkene, or alkyne. Examples ofalkyl groups include, but are not limited to, methyl; ethyls such asethanyl, ethenyl, and ethynyl; propyls such as propan-1-yl, propan-2-yl,prop-1-en-1-yl, prop-1-en-2-yl, prop-2-en-1-yl (allyl), prop-1-yn-1-yl,prop-2-yn-1-yl, etc.; butyls such as butan-1-yl, butan-2-yl,2-methyl-propan-1-yl, 2-methyl-propan-2-yl, but-1-en-1-yl,but-1-en-2-yl, 2-methyl-prop-1-en-1-yl, but-2-en-1-yl, but-2-en-2-yl,buta-1,3-dien-1-yl, buta-1,3-dien-2-yl, but-1-yn-1-yl, but-1-yn-3-yl,but-3-yn-1-yl, etc.; and the like.

Unless otherwise indicated, the term “alkyl” is specifically intended toinclude groups having any degree or level of saturation, i.e., groupshaving exclusively single carbon-carbon bonds, groups having one or moredouble carbon-carbon bonds, groups having one or more triplecarbon-carbon bonds, and groups having mixtures of single, double, andtriple carbon-carbon bonds. Where a specific level of saturation isintended, the terms “alkanyl,” “alkenyl,” and “alkynyl” are used. Incertain embodiments, an alkyl group comprises from 1 to 40 carbon atoms,in certain embodiments, from 1 to 22 or 1 to 18 carbon atoms, in certainembodiments, from 1 to 16 or 1 to 8 carbon atoms, and in certainembodiments from 1 to 6 or 1 to 3 carbon atoms. In certain embodiments,an alkyl group comprises from 8 to 22 carbon atoms, in certainembodiments, from 8 to 18 or 8 to 16. In some embodiments, the alkylgroup comprises from 3 to 20 or 7 to 17 carbons. In some embodiments,the alkyl group comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, or 22 carbon atoms.

“Aryl” by itself or as part of another substituent refers to amonovalent aromatic hydrocarbon radical derived by the removal of onehydrogen atom from a single carbon atom of a parent aromatic ringsystem. Aryl encompasses 5- and 6-membered carbocyclic aromatic rings,for example, benzene; bicyclic ring systems wherein at least one ring iscarbocyclic and aromatic, for example, naphthalene, indane, andtetralin; and tricyclic ring systems wherein at least one ring iscarbocyclic and aromatic, for example, fluorene. Aryl encompassesmultiple ring systems having at least one carbocyclic aromatic ringfused to at least one carbocyclic aromatic ring, cycloalkyl ring, orheterocycloalkyl ring. For example, aryl includes 5- and 6-memberedcarbocyclic aromatic rings fused to a 5- to 7-membered non-aromaticheterocycloalkyl ring containing one or more heteroatoms chosen from N,O, and S. For such fused, bicyclic ring systems wherein only one of therings is a carbocyclic aromatic ring, the point of attachment may be atthe carbocyclic aromatic ring or the heterocycloalkyl ring. Examples ofaryl groups include, but are not limited to, groups derived fromaceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene,benzene, chrysene, coronene, fluoranthene, fluorene, hexacene,hexaphene, hexalene, as-indacene, s-indacene, indane, indene,naphthalene, octacene, octaphene, octalene, ovalene, penta-2,4-diene,pentacene, pentalene, pentaphene, perylene, phenalene, phenanthrene,picene, pleiadene, pyrene, pyranthrene, rubicene, triphenylene,trinaphthalene, and the like. In certain embodiments, an aryl group cancomprise from 5 to 20 carbon atoms, and in certain embodiments, from 5to 12 carbon atoms. In certain embodiments, an aryl group can comprise5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbonatoms. Aryl, however, does not encompass or overlap in any way withheteroaryl, separately defined herein. Hence, a multiple ring system inwhich one or more carbocyclic aromatic rings is fused to aheterocycloalkyl aromatic ring, is heteroaryl, not aryl, as definedherein.

“Arylalkyl” by itself or as part of another substituent refers to anacyclic alkyl radical in which one of the hydrogen atoms bonded to acarbon atom, typically a terminal or sp³ carbon atom, is replaced withan aryl group. Examples of arylalkyl groups include, but are not limitedto, benzyl, 2-phenylethan-1-yl, 2-phenylethen-1-yl, naphthylmethyl,2-naphthylethan-1-yl, 2-naphthylethen-1-yl, naphthobenzyl,2-naphthophenylethan-1-yl, and the like. Where specific alkyl moietiesare intended, the nomenclature arylalkanyl, arylalkenyl, or arylalkynylis used. In certain embodiments, an arylalkyl group is C₇₋₃₀ arylalkyl,e.g., the alkanyl, alkenyl, or alkynyl moiety of the arylalkyl group isC₁₋₁₀ and the aryl moiety is C₆₋₂₀, and in certain embodiments, anarylalkyl group is C₇₋₂₀ arylalkyl, e.g., the alkanyl, alkenyl, oralkynyl moiety of the arylalkyl group is C₁₋₈ and the aryl moiety isC₆₋₁₂.

Estolide “base oil” and “base stock”, unless otherwise indicated, referto any composition comprising one or more estolide compounds. It shouldbe understood that an estolide “base oil” or “base stock” is not limitedto compositions for a particular use, and instead generally refer tocompositions comprising one or more estolides, including mixtures ofestolides. Estolide base oils and base stocks can also include compoundsother than estolides.

The term “catalyst” refers to single chemical species; physicalcombinations of chemical species, such as mixtures, alloys, and thelike; and combinations of one or more catalyst within the same region orlocation of a reactor or reaction vessel. Examples of catalyst include,e.g., Lewis acids, Bronsted acids, and Bismuth catalysts, wherein Lewisacids, Bronsted acids, and Bismuth catalysts may be single chemicalspecies; physical combinations of chemical species, such as mixtures,alloys, and the like; and combinations of one or more catalyst withinthe same region or location of a reactor or reaction vessel.

The term “continuous” as used herein means a process wherein reactantsare introduced and products withdrawn over a period of time during whichthe reaction continues without significant interruption. “Continuous” isnot meant in any way to prohibit normal interruptions in the continuityof the process due to, for example, start-up, reactor maintenance, orscheduled shut down periods. In addition, the term “continuous” mayinclude processes, wherein some of the reactants are charged at thebeginning of the process and the remaining reactants are fed into thereactor such that the levels of reactants support continuing reactionprocesses. “Continuous” further includes processes where one or morereactants are intermittently added.

“Compounds” refers to compounds encompassed by structural Formula I, II,and III herein and includes any specific compounds within the formulawhose structure is disclosed herein. Compounds may be identified eitherby their chemical structure and/or chemical name. When the chemicalstructure and chemical name conflict, the chemical structure isdeterminative of the identity of the compound. The compounds describedherein may contain one or more chiral centers and/or double bonds andtherefore may exist as stereoisomers such as double-bond isomers (i.e.,geometric isomers), enantiomers, or diastereomers. Accordingly, anychemical structures within the scope of the specification depicted, inwhole or in part, with a relative configuration encompass all possibleenantiomers and stereoisomers of the illustrated compounds including thestereoisomerically pure form (e.g., geometrically pure, enantiomericallypure, or diastereomerically pure) and enantiomeric and stereoisomericmixtures. Enantiomeric and stereoisomeric mixtures may be resolved intotheir component enantiomers or stereoisomers using separation techniquesor chiral synthesis techniques well known to the skilled artisan.

For the purposes of the present disclosure, “chiral compounds” arecompounds having at least one center of chirality (i.e. at least oneasymmetric atom, in particular at least one asymmetric C atom), havingan axis of chirality, a plane of chirality or a screw structure.“Achiral compounds” are compounds which are not chiral.

Compounds of Formulas I, II, and III include, but are not limited to,optical isomers of compounds of Formulas I, II, and III, racematesthereof, and other mixtures thereof. In such embodiments, the singleenantiomers or diastereomers, i.e., optically active forms, can beobtained by asymmetric synthesis or by resolution of the racemates.Resolution of the racemates may be accomplished by, for example,chromatography, using, for example a chiral high-pressure liquidchromatography (HPLC) column. However, unless otherwise stated, itshould be assumed that Formula I, II, and III covers all asymmetricvariants of the compounds described herein, including isomers,racemates, enantiomers, diastereomers, and other mixtures thereof. Inaddition, compounds of Formula I, II, and III include Z- and E-forms(e.g., cis- and trans-forms) of compounds with double bonds. Thecompounds of Formula I, II, and III may also exist in several tautomericforms including the enol form, the keto form, and mixtures thereof.Accordingly, the chemical structures depicted herein encompass allpossible tautomeric forms of the illustrated compounds.

“Cycloalkyl” by itself or as part of another substituent refers to asaturated or unsaturated cyclic alkyl radical. Where a specific level ofsaturation is intended, the nomenclature “cycloalkanyl” or“cycloalkenyl” is used. Examples of cycloalkyl groups include, but arenot limited to, groups derived from cyclopropane, cyclobutane,cyclopentane, cyclohexane, and the like. In certain embodiments, acycloalkyl group is C₃₋₁₅ cycloalkyl, and in certain embodiments, C₃₋₁₂cycloalkyl or C₅₋₁₂ cycloalkyl. In certain embodiments, a cycloalkylgroup is a C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, or C₁₅cycloalkyl.

“Cycloalkylalkyl” by itself or as part of another substituent refers toan acyclic alkyl radical in which one of the hydrogen atoms bonded to acarbon atom, typically a terminal or sp³ carbon atom, is replaced with acycloalkyl group. Where specific alkyl moieties are intended, thenomenclature cycloalkylalkanyl, cycloalkylalkenyl, or cycloalkylalkynylis used. In certain embodiments, a cycloalkylalkyl group is C₇₋₃₀cycloalkylalkyl, e.g., the alkanyl, alkenyl, or alkynyl moiety of thecycloalkylalkyl group is C₁₋₁₀ and the cycloalkyl moiety is C₆₋₂₀, andin certain embodiments, a cycloalkylalkyl group is C₇₋₂₀cycloalkylalkyl, e.g., the alkanyl, alkenyl, or alkynyl moiety of thecycloalkylalkyl group is C₁₋₈ and the cycloalkyl moiety is C₄₋₂₀ orC₆₋₁₂.

“Halogen” refers to a fluoro, chloro, bromo, or iodo group.

“Heteroaryl” by itself or as part of another substituent refers to amonovalent heteroaromatic radical derived by the removal of one hydrogenatom from a single atom of a parent heteroaromatic ring system.Heteroaryl encompasses multiple, ring systems having at least onearomatic ring fused to at least one other ring, which can be aromatic ornon-aromatic in which at least one ring atom is a heteroatom. Heteroarylencompasses 5- to 12-membered aromatic, such as 5- to 7-membered,monocyclic rings containing one or more, for example, from 1 to 4, or incertain embodiments, from 1 to 3, heteroatoms chosen from N, O, and S,with the remaining ring atoms being carbon; and bicyclicheterocycloalkyl rings containing one or more, for example, from 1 to 4,or in certain embodiments, from 1 to 3, heteroatoms chosen from N, O,and S, with the remaining ring atoms being carbon and wherein at leastone heteroatom is present in an aromatic ring. For example, heteroarylincludes a 5- to 7-membered heterocycloalkyl, aromatic ring fused to a5- to 7-membered cycloalkyl ring. For such fused, bicyclic heteroarylring systems wherein only one of the rings contains one or moreheteroatoms, the point of attachment may be at the heteroaromatic ringor the cycloalkyl ring. In certain embodiments, when the total number ofN, S, and O atoms in the heteroaryl group exceeds one, the heteroatomsare not adjacent to one another. In certain embodiments, the totalnumber of N, S, and O atoms in the heteroaryl group is not more thantwo. In certain embodiments, the total number of N, S, and O atoms inthe aromatic heterocycle is not more than one. Heteroaryl does notencompass or overlap with aryl as defined herein.

Examples of heteroaryl groups include, but are not limited to, groupsderived from acridine, arsindole, carbazole, β-carboline, chromane,chromene, cinnoline, furan, imidazole, indazole, indole, indoline,indolizine, isobenzofuran, isochromene, isoindole, isoindoline,isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole,oxazole, perimidine, phenanthridine, phenanthroline, phenazine,phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine,pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline, quinoline,quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene,triazole, xanthene, and the like. In certain embodiments, a heteroarylgroup is from 5- to 20-membered heteroaryl, and in certain embodimentsfrom 5- to 12-membered heteroaryl or from 5- to 10-membered heteroaryl.In certain embodiments, a heteroaryl group is a 5-, 6-, 7-, 8-, 9-, 10-,11-, 12-, 13-, 14-, 15-, 16-, 17-, 18-, 19-, or 20-membered heteroaryl.In certain embodiments heteroaryl groups are those derived fromthiophene, pyrrole, benzothiophene, benzofuran, indole, pyridine,quinoline, imidazole, oxazole, and pyrazine.

“Heteroarylalkyl” by itself or as part of another substituent refers toan acyclic alkyl radical in which one of the hydrogen atoms bonded to acarbon atom, typically a terminal or sp³ carbon atom, is replaced with aheteroaryl group. Where specific alkyl moieties are intended, thenomenclature heteroarylalkanyl, heteroarylalkenyl, or heteroarylalkynylis used. In certain embodiments, a heteroarylalkyl group is a 6- to30-membered heteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynylmoiety of the heteroarylalkyl is 1- to 10-membered and the heteroarylmoiety is a 5- to 20-membered heteroaryl, and in certain embodiments, 6-to 20-membered heteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynylmoiety of the heteroarylalkyl is 1- to 8-membered and the heteroarylmoiety is a 5- to 12-membered heteroaryl.

“Heterocycloalkyl” by itself or as part of another substituent refers toa partially saturated or unsaturated cyclic alkyl radical in which oneor more carbon atoms (and any associated hydrogen atoms) areindependently replaced with the same or different heteroatom. Examplesof heteroatoms to replace the carbon atom(s) include, but are notlimited to, N, P, O, S, Si, etc. Where a specific level of saturation isintended, the nomenclature “heterocycloalkanyl” or “heterocycloalkenyl”is used. Examples of heterocycloalkyl groups include, but are notlimited to, groups derived from epoxides, azirines, thiiranes,imidazolidine, morpholine, piperazine, piperidine, pyrazolidine,pyrrolidine, quinuclidine, and the like.

“Heterocycloalkylalkyl” by itself or as part of another substituentrefers to an acyclic alkyl radical in which one of the hydrogen atomsbonded to a carbon atom, typically a terminal or sp^(a) carbon atom, isreplaced with a heterocycloalkyl group. Where specific alkyl moietiesare intended, the nomenclature heterocycloalkylalkanyl,heterocycloalkylalkenyl, or heterocycloalkylalkynyl is used. In certainembodiments, a heterocycloalkylalkyl group is a 6- to 30-memberedheterocycloalkylalkyl, e.g., the alkanyl, alkenyl, or alkynyl moiety ofthe heterocycloalkylalkyl is 1- to 10-membered and the heterocycloalkylmoiety is a 5- to 20-membered heterocycloalkyl, and in certainembodiments, 6- to 20-membered heterocycloalkylalkyl, e.g., the alkanyl,alkenyl, or alkynyl moiety of the heterocycloalkylalkyl is 1- to8-membered and the heterocycloalkyl moiety is a 5- to 12-memberedheterocycloalkyl.

“Mixture” refers to a collection of molecules or chemical substances.Each component in a mixture can be independently varied. A mixture maycontain, or consist essentially of, two or more substances intermingledwith or without a constant percentage composition, wherein eachcomponent may or may not retain its essential original properties, andwhere molecular phase mixing may or may not occur. In mixtures, thecomponents making up the mixture may or may not remain distinguishablefrom each other by virtue of their chemical structure. “Parent aromaticring system” refers to an unsaturated cyclic or polycyclic ring systemhaving a conjugated π (pi) electron system. Included within thedefinition of “parent aromatic ring system” are fused ring systems inwhich one or more of the rings are aromatic and one or more of the ringsare saturated or unsaturated, such as, for example, fluorene, indane,indene, phenalene, etc. Examples of parent aromatic ring systemsinclude, but are not limited to, aceanthrylene, acenaphthylene,acephenanthrylene, anthracene, azulene, benzene, chrysene, coronene,fluoranthene, fluorene, hexacene, hexaphene, hexalene, as-indacene,s-indacene, indane, indene, naphthalene, octacene, octaphene, octalene,ovalene, penta-2,4-diene, pentacene, pentalene, pentaphene, perylene,phenalene, phenanthrene, picene, pleiadene, pyrene, pyranthrene,rubicene, triphenylene, trinaphthalene, and the like.

“Parent heteroaromatic ring system” refers to a parent aromatic ringsystem in which one or more carbon atoms (and any associated hydrogenatoms) are independently replaced with the same or different heteroatom.Examples of heteroatoms to replace the carbon atoms include, but are notlimited to, N, P, O, S, Si, etc. Specifically included within thedefinition of “parent heteroaromatic ring systems” are fused ringsystems in which one or more of the rings are aromatic and one or moreof the rings are saturated or unsaturated, such as, for example,arsindole, benzodioxan, benzofuran, chromane, chromene, indole,indoline, xanthene, etc. Examples of parent heteroaromatic ring systemsinclude, but are not limited to, arsindole, carbazole, β-carboline,chromane, chromene, cinnoline, furan, imidazole, indazole, indole,indoline, indolizine, isobenzofuran, isochromene, isoindole,isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine,oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline,phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole,pyridazine, pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline,quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole,thiophene, triazole, xanthene, and the like.

“Solid-supported acid” refers to an acidic compound or material that issupported by or attached to another compound or material comprising asolid or semi-solid structure. Such materials include smooth supports(e.g., metal, glass, plastic, silicon, carbon (e.g., diamond, graphite,nanotubes, fullerenes (e.g., C-60)) and ceramic surfaces) as well astextured and porous materials such as clays and clay-like materials.Such materials also include, but are not limited to, gels, rubbers,polymers, and other non-rigid materials. Solid supports need not becomposed of a single material. By way of example but not by way oflimitation, a solid support may comprise a surface material (e.g. alayer or coating) and a different supporting material (e.g., coatedglass, coated metals and plastics, etc.) In some embodiments,solid-supported acids comprise two or more different materials, e.g., inlayers. Surface layers and coatings may be of any configuration and maypartially or completely cover a supporting material. It is contemplatedthat solid supports may comprise any combination of layers, coatings, orother configurations of multiple materials. In some embodiments, asingle material provides essentially all of the surface to which othermaterial can be attached, while in other embodiments, multiple materialsof the solid support are exposed for attachment of another material.Solid supports need not be flat. Supports include any type of shapeincluding spherical shapes (e.g., beads). Acidic moieties attached tosolid support may be attached to any portion of the solid support (e.g.,may be attached to an interior portion of a porous solid supportmaterial). Exemplary solid-supported acids include, but are not limitedto, cation exchange resins (e.g., Amberlyst®, Dowex®); acid-activatedclays (e.g., montmorillonites); polymer-supported sulfonic acids (e.g.,Nafion®); and silica-support catalysts (e.g., SPA-2).

“Substituted” refers to a group in which one or more hydrogen atoms areindependently replaced with the same or different substituent(s).Examples of substituents include, but are not limited to, —R⁶⁴, —R⁶⁰,—O⁻, —OH, ═O, —OR⁶⁰, —SR⁶⁰, —S⁻, ═S, —NR⁶⁰R⁶¹, ═NR⁶⁰, —CN, —CF₃, —OCN,—SCN, —NO, —NO₂, ═N₂, —N₃, —S(O)₂O⁻, —S(O)₂OH, —S(O)₂R⁶⁰, —OS(O₂)O⁻,—OS(O)₂R⁶⁰, —P(O)(O⁻)₂, —P(O)(OR⁶⁰)(O⁻), —OP(O)(OR⁶⁰)(OR⁶¹), —C(O)R⁶⁰,—C(S)R⁶⁰, —C(O)OR⁶⁰, —C(O)NR⁶⁰R⁶¹, —C(O)O⁻, —C(S)OR⁶⁰, —NR⁶²C(O)NR⁶⁰R⁶¹,—NR⁶²C(S)NR⁶⁰R⁶¹, —NR⁶²C(NR⁶³)NR⁶⁰R⁶¹, —C(NR⁶²)NR⁶⁰R⁶¹, —S(O)₂NR⁶⁰R⁶¹,—NR⁶³S(O)₂R⁶⁰, —NR⁶³C(O)R⁶⁰, and —S(O)R⁶⁰;

wherein each —R⁶⁴ is independently a halogen; each R⁶⁰ and R⁶¹ areindependently alkyl, substituted alkyl, alkoxy, substituted alkoxy,cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substitutedheterocycloalkyl, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, arylalkyl, substituted arylalkyl, heteroarylalkyl, orsubstituted heteroarylalkyl, or R⁶⁰ and R⁶¹ together with the nitrogenatom to which they are bonded form a heterocycloalkyl, substitutedheterocycloalkyl, heteroaryl, or substituted heteroaryl ring, and R⁶²and R⁶³ are independently alkyl, substituted alkyl, aryl, substitutedaryl, arylalkyl, substituted arylalkyl, cycloalkyl, substitutedcycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, heteroaryl,substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl,or R⁶² and R⁶³ together with the atom to which they are bonded form oneor more heterocycloalkyl, substituted heterocycloalkyl, heteroaryl, orsubstituted heteroaryl rings;

wherein the “substituted” substituents, as defined above for R⁶⁰, R⁶¹,R⁶², and R⁶³, are substituted with one or more, such as one, two, orthree, groups independently selected from alkyl, -alkyl-OH,—O-haloalkyl, -alkyl-NH₂, alkoxy, cycloalkyl, cycloalkylalkyl,heterocycloalkyl, heterocycloalkylalkyl, aryl, heteroaryl, arylalkyl,heteroarylalkyl, —O⁻, —OH, ═O, —O-alkyl, —O-aryl, —O-heteroarylalkyl,—O-cycloalkyl, —O-heterocycloalkyl, —SH, —S⁻, ═S, —S-alkyl, —S-aryl, —S—heteroarylalkyl, —S-cycloalkyl, —S-heterocycloalkyl, —NH₂, ═NH, —CN,—CF₃, —OCN, —SCN, —NO, —NO₂, ═N₂, —N₃, —S(O)₂O⁻, —S(O)₂, —S(O)₂OH,—OS(O₂)O⁻, —SO₂(alkyl), —SO₂(phenyl), —SO₂(haloalkyl), —SO₂NH₂,—SO₂NH(alkyl), —SO₂NH(phenyl), —P(O)(O⁻)₂, —P(O)(O-alkyl)(O⁻),—OP(O)(O-alkyl)(O-alkyl), —CO₂H, —C(O)O(alkyl), —CON(alkyl)(alkyl),—CONH(alkyl), —CONH₂, —C(O)(alkyl), —C(O)(phenyl), —C(O)(haloalkyl),—OC(O)(alkyl), —N(alkyl)(alkyl), —NH(alkyl), —N(alkyl)(alkylphenyl),—NH(alkylphenyl), —NHC(O)(alkyl), —NHC(O)(phenyl), —N(alkyl)C(O)(alkyl),and —N(alkyl)C(O)(phenyl).

As used in this specification and the appended claims, the articles “a,”“an,” and “the” include plural referents unless expressly andunequivocally limited to one referent.

The term “fatty acid” refers to any natural or synthetic carboxylic acidcomprising an alkyl chain that may be saturated, monounsaturated, orpolyunsaturated, and may have straight or branched chains. The fattyacid may also be substituted. “Fatty acid,” as used herein, includesshort chain alkyl carboxylic acid including, for example, acetic acid,propionic acid, etc.

The term “fatty acid reactant” refers to any compound or compositioncomprising a fatty acid residue that is capable of undergoingoligomerization with another fatty acid or fatty acid reactant. Forexample, in certain embodiments, the fatty acid reactant may comprise asaturated or unsaturated fatty acid or fatty acid oligomer. In certainembodiments, a fatty acid oligomer may comprise a first fatty acid thathas previously undergone oligomerization with one or more second fattyacids to form an estolide, such as an estolide having a low EN (e.g.,dimer). It is understood that a “first” fatty acid reactant can comprisethe same structure as a “second” fatty acid reactant. For example, incertain embodiments, a reaction mixture may only comprise oleic acid,wherein the first fatty acid reactant and second fatty acid reactant areboth oleic acid.

The term “acid-activated clay” refers to clays that are derived from thenaturally occurring ore bentonite or the mineral montmorillonite andincludes materials prepared by calcination, washing or leaching withmineral acid, ion exchange or any combination thereof, includingmaterials which are often called montmorillonites, acid-activatedmontmorillonites and activated montmorillonites. In certain embodiments,these clays may contain Bronsted as well as Lewis acid active sites withmany of the acidic sites located within the clay lattice. Such claysinclude, but are not limited to the materials denoted as montmorilloniteK10, montmorillonite clay, clayzic, clayfen, the Engelhardt series ofcatalysts related to and including X-9107, X9105, Girdler KSF, Tonsiland K-catalysts derived from montmorillonite, including but not limitedto K5, K10, K20 and K30, KSF, KSF/O, and KP10. Other acid-activatedclays may include X-9105 and X-9107 acid washed clay catalysts marketedby Engelhard.

The term “zeolite” refers to mesoporous aluminosilicates of the group IAor group HA elements and are related to montmorillonite clays that areor have been acid activated. Zeolites may comprise what is considered an“infinitely” extending framework of AlO4 and SiO4 tetrahedra linked toeach other by the sharing of oxygens. The framework structure maycontain channels or interconnecting voids that are occupied by cationsand water molecules. Acidic character may be imparted or enhanced by ionexchange of the cations, such as with ammonium ions and subsequentthermal deamination or calcination. The acidic sites may primarily belocated within the lattice pores and channels. In certain instances,zeolites include, but are not limited to, the beta-type zeolites astypified by CP814E manufactured by Zeolyst International, the mordeniteform of zeolites as typified by CBV21A manufactured by ZeolystInternational, the Y-type zeolites as typified by CBV-720 manufacturedby Zeolyst International, and the ZSM family of zeolites as typified byZSM-5, and ZSM-11.

All numerical ranges herein include all numerical values and ranges ofall numerical values within the recited range of numerical values.

The present disclosure relates to estolide compounds, compositions andmethods of making the same. In certain embodiments, the estolidecompounds and compositions are useful as estolide base oil or estolidebase oil feedstock. In certain embodiments, the present disclosurerelates to processes for preparing estolides that utilize catalysts thatcan be recovered and reused. In certain embodiments, the presentdisclosure relates to efficient continuous and semi-continuous flowprocesses for preparing estolide base oils, base stocks, and lubricants.In certain embodiments, the present disclosure relates to catalysts thatcan be recovered and reused and/or used in efficient continuous andsemi-continuous flow processes. In certain embodiments, the catalystsand methods disclosed herein may be useful in preparing an estolidecompound of Formula I:

wherein

x is, independently for each occurrence, an integer selected from 0, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20;

y is, independently for each occurrence, an integer selected from 0, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20;

n is an integer selected from 1 to 12;

R₁ is an optionally substituted alkyl that is saturated or unsaturated,and branched or unbranched; and

R₂ is selected from hydrogen and optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched;

wherein each fatty acid chain residue of said at least one compound isindependently optionally substituted.

In certain embodiments, the catalysts and methods disclosed herein maybe useful in preparing an estolide compound of Formula II

wherein

n is an integer greater than or equal to 1;

R₂ is selected from hydrogen and optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched; and

R₁, R₃, and R₄, independently for each occurrence, are selected fromoptionally substituted alkyl that is saturated or unsaturated, andbranched or unbranched.

In certain embodiments, the catalysts and methods disclosed herein maybe useful in preparing an estolide compound of Formula III:

wherein

x is, independently for each occurrence, an integer selected from 0, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20;

y is, independently for each occurrence, an integer selected from 0, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20;

n is equal to or greater than 0;

R₁ is an optionally substituted alkyl that is saturated or unsaturated,and branched or unbranched; and

R₂ is selected from hydrogen and optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched;

wherein each fatty acid chain residue of said at least one compound isindependently optionally substituted.

The term “chain”, or “fatty acid chain,” or “fatty acid chain residue,”as used with respect to the estolide compounds of Formula I, II, and IIIrefer to one or more of the fatty acid residues incorporated in estolidecompounds, e.g., R₃ or R₄ of Formula II, or the structures representedby CH₃(CH₂)_(y)CH(CH₂)_(x)C(O)O— in Formula I or III.

The R₁ in Formula I, 11, and In at the top of each Formula shown is anexample of what may be referred to as a “cap” or “capping material,” asit “caps” the top of the estolide. Similarly, the capping group may bean organic acid residue of general formula —OC(O)-alkyl, i.e., acarboxylic acid with a substituted or unsubstituted, saturated orunsaturated, and/or branched or unbranched alkyl as defined herein, or aformic acid residue. In certain embodiments, the “cap” or “cappinggroup” is a fatty acid. In certain embodiments, the capping group,regardless of size, is substituted or unsubstituted, saturated orunsaturated, and/or branched or unbranched. The cap or capping materialmay also be referred to as the primary or alpha (a) chain.

Depending on the manner in which the estolide is synthesized, the cap orcapping group alkyl may be the only alkyl from an organic acid residuein the resulting estolide that is unsaturated. In certain embodiments,it may be desirable to use a saturated organic or fatty-acid cap toincrease the overall saturation of the estolide and/or to increase theresulting estolide's stability. For example, in certain embodiments, itmay be desirable to provide a method of providing a saturated cappedestolide by hydrogenating an unsaturated cap using any suitable methodsavailable to those of ordinary skill in the art. Hydrogenation may beused with various sources of the fatty-acid feedstock, which may includemono- and/or polyunsaturated fatty acids. Without being bound to anyparticular theory, in certain embodiments, hydrogenating the estolidemay help to improve the overall stability of the molecule. However, afully-hydrogenated estolide, such as an estolide with a larger fattyacid cap, may exhibit increased pour point temperatures. In certainembodiments, it may be desirable to offset any loss in desirablepour-point characteristics by using shorter, saturated cappingmaterials.

The R₄C(O)O— of Formula II or the CH₃(CH₂)_(y)CH(CH₂)—C(O)O— of FormulaI and DI serve as the “base” or “base chain residue” of the estolide.Depending on the manner in which the estolide is synthesized, the baseorganic acid or fatty acid residue may be the only residue that remainsin its free-acid form after the initial synthesis of the estolide.However, in an effort to alter or improve the properties of theestolide, in certain embodiments, the free acid may be reacted with anynumber of substituents. For example, in certain embodiments, it may bedesirable to react the free acid estolide with alcohols, glycols,amines, or other suitable reactants to provide the corresponding ester,amide, or other reaction products. The base or base chain residue mayalso be referred to as tertiary or gamma (γ) chains.

The R₃C(O)O— of Formula II or structure CH₃(CH₂)_(y)CH(CH₂)_(x)C(O)O— ofFormula I and DI are linking residues that link the capping material andthe base fatty-acid residue together. There may be any number of linkingresidues in the estolide, including when n=0 and the estolide is in itsdimer form. Depending on the manner in which the estolide is prepared,in certain embodiments, a linking residue may be a fatty acid and mayinitially be in an unsaturated form during synthesis. In someembodiments, the estolide will be formed when a catalyst is used toproduce a carbocation at the fatty acid's site of unsaturation, which isfollowed by nucleophilic attack on the carbocation by the carboxylicgroup of another fatty acid. In some embodiments, it may be desirable tohave a linking fatty acid that is monounsaturated so that when the fattyacids link together, all of the sites of unsaturation are eliminated.The linking residue(s) may also be referred to as secondary or beta (β)chains.

In certain embodiments, the cap is an acetyl group, the linkingresidue(s) is one or more fatty acid residues, and the base chainresidue is a fatty acid residue. In certain embodiments, the linkingresidues present in an estolide differ from one another. In certainembodiments, one or more of the linking residues differs from the basechain residue.

In some embodiments, the estolide comprises fatty-acid chains of varyinglengths. In some embodiments with estolides according to Formula I andIII, x is, independently for each occurrence, an integer selected from 0to 20, 0 to 18, 0 to 16, 0 to 14, 1 to 12, 1 to 10, 2 to 8, 6 to 8, or 4to 6. In some embodiments with estolides according to Formula I and DI,x is, independently for each occurrence, an integer selected from 7 and8. In some embodiments with estolides according to Formula I, x is,independently for each occurrence, an integer selected from 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

In some embodiments with estolides according to Formula I and DI, y is,independently for each occurrence, an integer selected from 0 to 20, 0to 18, 0 to 16, 0 to 14, 1 to 12, 1 to 10, 2 to 8, 6 to 8, or 4 to 6. Insome embodiments with estolides according to Formula I and DI, y is,independently for each occurrence, an integer selected from 7 and 8. Insome embodiments with estolides according to Formula I, y is,independently for each occurrence, an integer selected from 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. In someembodiments with estolides according to Formula I, x+y is, independentlyfor each chain, an integer selected from 0 to 40, 0 to 20, 10 to 20, or12 to 18. In some embodiments with estolides according to Formula I andx+y is, independently for each chain, an integer selected from 13 to 15.In some embodiments with estolides according to Formula I and III, x+yis 15. In some embodiments with estolides according to Formula I, x+yis, independently for each chain, an integer selected from 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or40.

In some embodiments, the estolide of Formula I, II, or III may compriseany number of fatty acid residues to form an “n-mer” estolide. Forexample, the estolide may be in its dimer (n=0), trimer (n=1), tetramer(n=2), pentamer (n=3), hexamer (n=4), heptamer (n=5), octamer (n=6),nonamer (n=7), or decamer (n=8) form. In some embodiments, n is aninteger selected from 0 to 20, 0 to 18, 0 to 16, 0 to 14, 0 to 12, 0 to10, 0 to 8, or 0 to 6. In some embodiments, n is an integer selectedfrom 0 to 4. In some embodiments, n is 1, wherein said at least onecompound of Formula I, II, and III comprises the trimer. In someembodiments, n is an integer selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

In some embodiments, R₁ of Formula I, II, or III is an optionallysubstituted alkyl that is saturated or unsaturated, and branched orunbranched. In some embodiments, the alkyl group is a C₁ to C₄₀ alkyl,C₁ to C₂₂ alkyl or C₁ to C₁₈ alkyl. In some embodiments, the alkyl groupis selected from C₇ to C₁₇ alkyl. In some embodiments, R₁ is selectedfrom C₇ alkyl, C₉ alkyl, C₁₁ alkyl, C₁₃ alkyl, C₁₅ alkyl, and C₁₇ alkyl.In some embodiments, R₁ is selected from C₁₃ to C₁₇ alkyl, such as fromC₁₃ alkyl, C₁₅ alkyl, and C₁₇ alkyl. In some embodiments, R₁ is a C₁,C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇,C₁₈, C₁₉, C₂₀, C₂₁, or C₂₂ alkyl.

In some embodiments, R₂ of Formula I, II, or DI is an optionallysubstituted alkyl that is saturated or unsaturated, and branched orunbranched. In some embodiments, the alkyl group is a C₁ to C₄₀alkyl, C₁to C₂₂ alkyl or C₁ to C₁₈ alkyl. In some embodiments, the alkyl group isselected from C₇ to C₁₇ alkyl. In some embodiments, R₂ is selected fromC₇ alkyl, C₉ alkyl, C₁₁ alkyl, C₁₃ alkyl, C₁₅ alkyl, and C₁₇ alkyl. Insome embodiments, R₂ is selected from C₁₃ to C₁₇ alkyl, such as from C₁₃alkyl, C₁₅ alkyl, and C₁₇ alkyl. In some embodiments, R₂ is a C₁, C₂,C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈,C₁₉, C₂₀, C₂₁, or C₂₂ alkyl.

In some embodiments, R₃ is an optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched. In someembodiments, the alkyl group is a C₁ to C₄₀ alkyl, C₁ to C₂₂ alkyl or C₁to C₁₈ alkyl. In some embodiments, the alkyl group is selected from C₇to C₁₇ alkyl. In some embodiments, R₃ is selected from C₇ alkyl, C₉alkyl, C₁₁ alkyl, C₁₃ alkyl, C₁₅ alkyl, and C₁₇ alkyl. In someembodiments, R₃ is selected from C₁₃ to C₁₇ alkyl, such as from C₁₃alkyl, C₁₅ alkyl, and C₁₇ alkyl. In some embodiments, R₃ is a C₁, C₂,C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈,C₁₉, C₂₀, C₂₁, or C₂₂ alkyl.

In some embodiments, R₄ is an optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched. In someembodiments, the alkyl group is a C₁ to C₄₀ alkyl, C₁ to C₂₂ alkyl or C₁to C₁₈ alkyl. In some embodiments, the alkyl group is selected from C₇to C₁₇ alkyl. In some embodiments, R₄ is selected from C₇ alkyl, C₉alkyl, C₁₁ alkyl, C₁₃ alkyl, C₁₅ alkyl, and C₁₇ alkyl. In someembodiments, R₄ is selected from C₁₃ to C₁₇ alkyl, such as from C₁₃alkyl, C₁₅ alkyl, and C₁₇ alkyl. In some embodiments, R₄ is a C₁, C₂,C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈,C₁₉, C₂₀, C₂₁, or C₂₂ alkyl. As noted above, in certain embodiments, oneor more of the estolides' properties is manipulated by altering thelength of R₁ and/or its degree of saturation. In certain embodiments,the level of substitution on R₁ may also be altered to change or evenimprove the estolides' properties. Without being bound to any particulartheory, in certain embodiments, including polar substituents on R₁, suchas one or more hydroxy groups, may increase the viscosity of theestolide, while increasing pour point. Accordingly, in some embodiments,R₁ will be unsubstituted or optionally substituted with a group that isnot hydroxyl.

In some embodiments, the estolide is in its free-acid form, wherein R₂of Formulas I, II, and III is hydrogen. In some embodiments, R₂ isselected from optionally substituted alkyl that is saturated orunsaturated, and branched or unbranched. In some embodiments, the R₂residue may comprise any desired alkyl group, such as those derived fromesterification of the estolide with the alcohols identified in theexamples herein. In some embodiments, the alkyl group is selected fromC₁ to C₄₀, C₁ to C₂₂, C₃ to C₂₀, C₁ to C₁₈, or C₆ to C₁₂ alkyl. In someembodiments, R₂ may be selected from C₃ alkyl, C₄ alkyl, C₈ alkyl, C₁₂alkyl, C₁₆ alkyl, C₁₈ alkyl, and C₂₀ alkyl. For example, in someembodiments, R₂ may be branched, such as isopropyl, isobutyl, or2-ethylhexyl. In some embodiments, R₂ may be a larger alkyl group,branched or unbranched, comprising C₁₂ alkyl, C₁₆ alkyl, C₁₈ alkyl, orC₂₀ alkyl. In some embodiments, R₂ is a C₁, C₂, C₃, C₄, C₅, C₆, C₇, C₈,C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, C₁₉, C₂₀, C₂₁, or C₂₂alkyl. Such groups at the R₂ position may be derived from esterificationof the free-acid estolide using the Jarcol™ line of alcohols marketed byJarchem Industries, Inc. of Newark, N.J., including Jarcol™ I-18CG,I-20, I-12, I-16, I-18T, and 85BJ. In some cases, R₂ may be sourced fromcertain alcohols to provide branched alkyls such as isostearyl andisopalmityl. It should be understood that such isopalmityl andisostearyl akyl groups may cover any branched variation of C₁₆ and C₁₈,respectively. For example, the estolides described herein may comprisehighly-branched isopalmityl or isostearyl groups at the R₂ position,derived from the Fineoxocol® line of isopalmityl and isostearyl alcoholsmarketed by Nissan Chemical America Corporation of Houston, Tex.,including Fineoxocol® 180, 180N, and 1600. Without being bound to anyparticular theory, in certain embodiments, large, highly-branched alkylgroups (e.g., isopalmityl and isostearyl) at the R₂ position of theestolides can provide at least one way to increase the lubricant'sviscosity, while substantially retaining or even reducing its pourpoint.

In some embodiments, the compounds described herein may comprise amixture of two or more estolide compounds of Formula I, II, or III. Itis possible to characterize the chemical makeup of an estolide, amixture of estolides, or a composition comprising estolides, by usingthe compound's, mixture's, or composition's measured estolide number(EN). The EN represents the average number of fatty acids added to thebase fatty acid. The EN also represents the average number of estolidelinkages per molecule:

EN=n+1

wherein n is the number of secondary (β) fatty acids. Accordingly, asingle estolide compound will have an EN that is a whole number, forexample for dimers, trimers, and tetramers:

-   -   dimer EN=1    -   trimer EN=2    -   tetramer EN=3

However, a composition comprising two or more estolide compounds mayhave an EN that is a whole number or a fraction of a whole number. Forexample, a composition having a 1:1 molar ratio of dimer and trimerwould have an EN of 1.5, while a composition having a 1:1 molar ratio oftetramer and trimer would have an EN of 2.5.

In some embodiments, the compositions described herein may comprise amixture of two or more estolides having an EN that is an integer orfraction of an integer that is greater than 4.5, or even 5.0. In someembodiments, the EN may be an integer or fraction of an integer selectedfrom about 1.0 to about 5.0. In some embodiments, the EN is an integeror fraction of an integer selected from 1.2 to about 4.5. In someembodiments, the EN is selected from a value greater than 1.0, 1.2, 1.4,1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4,4.6, 4.8, 5.0, 5.2, 5.4, 5.6, and 5.8. In some embodiments, the EN isselected from a value less than 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6,2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4,5.6, 5.8, and 6.0. In some embodiments, the EN is selected from 1, 1.2,1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0,4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, and 6.0.

As noted above, it should be understood that the chains of the estolidecompounds may be independently optionally substituted, wherein one ormore hydrogens are removed and replaced with one or more of thesubstituents identified herein. Similarly, two or more of the hydrogenresidues may be removed to provide one or more sites of unsaturation,such as a cis or trans double bond. Further, the chains may optionallycomprise branched hydrocarbon residues. In some embodiments theestolides described herein may comprise at least one compound of FormulaII:

wherein

n is greater than or equal to 1;

R₂ is selected from hydrogen and optionally substituted alkyl that issaturated or unsaturated, and branched or unbranched; and

R₁, R₃ and R₄, independently for each occurrence, are selected fromoptionally substituted alkyl that is saturated or unsaturated, andbranched or unbranched.

In some embodiments, n is an integer selected from 1 to 20. In someembodiments, n is an integer selected from 1 to 12. In some embodiments,n is an integer selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19 and 20. In some embodiments, one or more R3differs from one or more other R3 in a compound of Formula II. In someembodiments, one or more R3 differs from R4 in a compound of Formula II.In some embodiments, if the compounds of Formula II are prepared fromone or more polyunsaturated fatty acids, it is possible that one or moreof R1, R3 and R4 will have one or more sites of unsaturation. In someembodiments, if the compounds of Formula II are prepared from one ormore branched fatty acids, it is possible than one or more of R1, R3,and R4 will be branched.

In some embodiments, R3 and R4 can be CH3(CH2)yCH(CH2)x-, where x is,independently for each occurrence, an integer selected from 0, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20, and yis, independently for each occurrence, an integer selected from 0, 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.Where both R3 and R4 are CH3(CH2)yCH(CH2)x-, the compounds may becompounds according to Formula I and

Without being bound to any particular theory, in certain embodiments,altering the EN to produce estolides having desired viscometricproperties while substantially retaining or even reducing pour point.For example, in some embodiments, exhibit a decreased pour point uponincreasing the EN value. Accordingly, in certain embodiments, a methodis provided for retaining or decreasing the pour point of an estolidebase oil, or a method is provided for retaining or decreasinig the pourpoint of a composition comprising an estolide base oil by increasing theEN of the base oil. In some embodiments, the method comprises: selectingan estolide base oil having an initial EN and an initial pour point; andremoving at least a portion of the base oil, said portion exhibiting anEN that is less than the initial EN of the base oil, wherein theresulting estolide base oil exhibits an EN that is greater than theinitial EN of the base oil, and a pour point that is equal to or lowerthan the initial pour point of the base oil. In some embodiments, theselected estolide base oil is prepared by oligomerizing at least onefirst unsaturated fatty acid with at least one second unsaturated fattyacid and/or saturated fatty acid. In some embodiments, the removing atleast a portion of the base oil is accomplished by distillation,chromatography, membrane separation, phase separation, affinityseparation, solvent extraction, or combinations thereof. In someembodiments, the distillation takes place at a temperature and/orpressure that is suitable to separate the estolide base oil intodifferent “cuts” that individually exhibit different EN values. In someembodiments, this may be accomplished by subjecting the base oiltemperature of at least about 250° C. and an absolute pressure of nogreater than about 25 microns. In some embodiments, the distillationtakes place at a temperature range of about 250° C. to about 310° C. andan absolute pressure range of about 10 microns to about 25 microns.

In some embodiments, estolide compounds and compositions exhibit an ENthat is greater than or equal to 1, such as an integer or fraction of aninteger selected from about 1.0 to about 2.0. In some embodiments, theEN is an integer or fraction of an integer selected from about 1.0 toabout 1.6. In some embodiments, the EN is a fraction of an integerselected from about 1.1 to about 1.5. In some embodiments, the EN isselected from a value greater than 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, and 1.9. In some embodiments, the EN is selected from a valueless than 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0.

In some embodiments, the EN is greater than or equal to 1.5, such as aninteger or fraction of an integer selected from about 1.8 to about 2.8.In some embodiments, the EN is an integer or fraction of an integerselected from about 2.0 to about 2.6. In some embodiments, the EN is afraction of an integer selected from about 2.1 to about 2.5. In someembodiments, the EN is selected from a value greater than 1.8, 1.9, 2.0,2.1, 2.2, 2.3, 2.4, 2.5, 2.6, and 2.7. In some embodiments, the EN isselected from a value less than 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6,2.7, and 2.8. In some embodiments, the EN is about 1.8, 2.0, 2.2, 2.4,2.6, or 2.8.

In some embodiments, the EN is greater than or equal to about 3, such asan integer or fraction of an integer selected from about 3.0 to about4.0. In some embodiments, the EN is a fraction of an integer selectedfrom about 3.2 to about 3.8. In some embodiments, the EN is a fractionof an integer selected from about 3.3 to about 3.7. In some embodiments,the EN is selected from a value greater than 3.0, 3.1, 3.2, 3.3, 3.4,3.5, 3.6, 3.7, 3.8, and 3.9. In some embodiments, the EN is selectedfrom a value less than 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, and4.0. In some embodiments, the EN is about 3.0, 3.2, 3.4, 3.6, 3.8, or4.0. In some embodiments, the EN is greater than or equal to about 4,such as an integer or fraction of an integer selected from about 4.0 toabout 5.0. In some embodiments, the EN is a fraction of an integerselected from about 4.2 to about 4.8. In some embodiments, the EN is afraction of an integer selected from about 4.3 to about 4.7. In someembodiments, the EN is selected from a value greater than 4.0, 4.1, 4.2,4.3, 4.4, 4.5, 4.6, 4.7, 4.8, and 4.9. In some embodiments, the EN isselected from a value less than 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8,4.9, and 5.0. In some embodiments, the EN is about 4.0, 4.2, 4.4, 4.6,4.8, or 5.0.

In some embodiments, the EN is greater than or equal to about 5, such asan integer or fraction of an integer selected from about 5.0 to about6.0. In some embodiments, the EN is a fraction of an integer selectedfrom about 5.2 to about 5.8. In some embodiments, the EN is a fractionof an integer selected from about 5.3 to about 5.7. In some embodiments,the EN is selected from a value greater than 5.0, 5.1, 5.2, 5.3, 5.4,5.5, 5.6, 5.7, 5.8, and 5.9. In some embodiments, the EN is selectedfrom a value less than 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, and6.0. In some embodiments, the EN is selected from a value less than 5.1,5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, and 6.0. In some embodiments,the EN is about 5.0, 5.2; 5.4, 5.4, 5.6, 5.8, or 6.0.

Typically, estolide base oil exhibit certain lubricity, viscosity,and/or pour point characteristics. For example, suitable viscositycharacteristics of the base oil may range from about 10 cSt to about 250cSt at 40° C., and/or about 3 cSt to about 30 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 50 cSt to about 150 cSt at 40° C., and/or about 10 cStto about 20 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscosities lessthan about 55 cSt at 40° C. or less than about 45 cSt at 40° C., and/orless than about 12 cSt at 100° C. or less than about 10 cSt at 100° C.In some embodiments, the estolide base oil may exhibit viscositieswithin a range from about 25 cSt to about 55 cSt at 40° C., and/or about5 cSt to about 11 cSt at 100° C. In some embodiments, the estolide baseoil may exhibit viscosities within a range from about 35 cSt to about 45cSt at 40° C., and/or about 6 cSt to about 10 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 38 cSt to about 43 cSt at 40° C., and/or about 7 cSt toabout 9 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscosities lessthan about 120 cSt at 40° C. or less than about 100 cSt at 40° C.,and/or less than about 18 cSt at 100° C. or less than about 17 cSt at100° C. In some embodiments, the estolide base oil may exhibit aviscosity within a range from about 70 cSt to about 120 cSt at 40° C.,and/or about 12 cSt to about 18 cSt at 100° C. In some embodiments, theestolide base oil may exhibit viscosities within a range from about 80cSt to about 100 cSt at 40° C., and/or about 13 cSt to about 17 cSt at100° C. In some embodiments, the estolide base oil may exhibitviscosities within a range from about 85 cSt to about 95 cSt at 40° C.,and/or about 14 cSt to about 16 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscositiesgreater than about 180 cSt at 40° C. or greater than about 200 cSt at40° C., and/or greater than about 20 cSt at 100° C. or greater thanabout 25 cSt at 100° C. In some embodiments, the estolide base oil mayexhibit a viscosity within a range from about 180 cSt to about 230 cStat 40° C., and/or about 25 cSt to about 31 cSt at 100° C. In someembodiments, estolide base oil may exhibit viscosities within a rangefrom about 200 cSt to about 250 cSt at 40° C., and/or about 25 cSt toabout 35 cSt at 100° C. In some embodiments, estolide base oil mayexhibit viscosities within a range from about 210 cSt to about 230 cStat 40° C., and/or about 28 cSt to about 33 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 200 cSt to about 220 cSt at 40° C., and/or about 26 cStto about 30 cSt at 100° C. In some embodiments, the estolide base oilmay exhibit viscosities within a range from about 205 cSt to about 215cSt at 40° C., and/or about 27 cSt to about 29 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscosities lessthan about 45 cSt at 40° C. or less than about 38 cSt at 40° C., and/orless than about 10 cSt at 100° C. or less than about 9 cSt at 100° C. Insome embodiments, the estolide base oil may exhibit a viscosity within arange from about 20 cSt to about 45 cSt at 40° C., and/or about 4 cSt toabout 10 cSt at 100° C. In some embodiments, the estolide base oil mayexhibit viscosities within a range from about 28 cSt to about 38 cSt at40° C., and/or about 5 cSt to about 9 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 30 cSt to about 35 cSt at 40° C., and/or about 6 cSt toabout 8 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscosities lessthan about 80 cSt at 40° C. or less than about 70 cSt at 40° C., and/orless than about 14 cSt at 100° C. or less than about 13 cSt at 100° C.In some embodiments, the estolide base oil may exhibit a viscositywithin a range from about 50 cSt to about 80 cSt at 40° C., and/or about8 cSt to about 14 cSt at 100° C. In some embodiments, the estolide baseoil may exhibit viscosities within a range from about 60 cSt to about 70cSt at 40° C., and/or about 9 cSt to about 13 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 63 cSt to about 68 cSt at 40° C., and/or about 10 cStto about 12 cSt at 100° C.

In some embodiments, the estolide base oil may exhibit viscositiesgreater than about 120 cSt at 40° C. or greater than about 130 cSt at40° C., and/or greater than about 15 cSt at 100° C. or greater thanabout 18 cSt at 100° C. In some embodiments, the estolide base oil mayexhibit a viscosity within a range from about 120 cSt to about 150 cStat 40° C., and/or about 16 cSt to about 24 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 130 cSt to about 160 cSt at 40° C., and/or about 17 cStto about 28 cSt at 100° C. In some embodiments, the estolide base oilmay exhibit viscosities within a range from about 130 cSt to about 145cSt at 40° C., and/or about 17 cSt to about 23 cSt at 100° C. In someembodiments, the estolide base oil may exhibit viscosities within arange from about 135 cSt to about 140 cSt at 40° C., and/or about 19 cStto about 21 cSt at 100° C.

The estolides may exhibit desirable low-temperature pour pointproperties. In some embodiments, the estolide base oil may exhibit apour point lower than about −25° C., about −35° C., −40° C., or evenabout −50° C. In some embodiments, the estolides have a pour point ofabout −25° C. to about −45° C. In some embodiments, the pour point fallswithin a range of about −30° C. to about −40° C., about −34° C. to about−38° C., about −30° C. to about −45° C., −35° C. to about −45° C., 34°C. to about −42° C., about −38° C. to about −42° C., or about 36° C. toabout −40° C. In some embodiments, the pour point falls within the rangeof about −27° C. to about −37° C., or about −30° C. to about −34° C. Insome embodiments, the pour point falls within the range of about −25° C.to about −35° C., or about −28° C. to about −32° C. In some embodiments,the pour point falls within the range of about −28° C. to about −38° C.,or about −31° C. to about −35° C. In some embodiments, the pour pointfalls within the range of about −31° C. to about −41° C., or about −34°C. to about −38° C. In some embodiments, the pour point falls within therange of about −40° C. to about −50° C., or about −42° C. to about −48°C. In some embodiments, the pour point falls within the range of about−50° C. to about −60° C., or about −52° C. to about −58° C. In someembodiments, the upper bound of the pour point is less than about −35°C., about −36° C. about −37° C., about −38° C., about −39° C., about−40° C., about −41° C., about −42° C., about −43° C., about −44° C., andabout −45° C. In some embodiments, the lower bound of the pour point isgreater than about −55° C., about −54° C., about −53° C., about −52° C.,−51, about −50° C., about −49° C., about −48° C., about −47° C., about−46° C., or about −45° C.

In addition, in certain embodiments, estolides may exhibit decreasedIodine Values (IV) when compared to estolides prepared by other methods.IV is a measure of the degree of total unsaturation of an oil, and isdetermined by measuring the amount of iodine per gram of estolide(cg/g). In certain instances, oils having a higher degree ofunsaturation may be more susceptible to creating corrosiveness anddeposits, and may exhibit lower levels of oxidative stability. Compoundshaving a higher degree of unsaturation will have more points ofunsaturation for iodine to react with, resulting in a higher N. Thus, incertain embodiments, it may be desirable to reduce the N of theestolides in an effort to increase the oil's oxidative stability, whilealso decreasing harmful deposits and the corrosiveness of the oil.

In some embodiments, estolide compounds and compositions have an IV ofless than about 40 cg/g or less than about 35 cg/g. In some embodiments,estolides have an N of less than about 30 cg/g, less than about 25 cg/g,less than about 20 cg/g, less than about 15 cg/g, less than about 10cg/g, or less than about 5 cg/g. The N of a composition may be reducedby decreasing the estolide's degree of unsaturation. In certainembodiments, this may be accomplished by, for example, by increasing theamount of saturated capping materials relative to unsaturated cappingmaterials when synthesizing the estolides. Alternatively, in certainembodiments, IV may be reduced by hydrogenating estolides havingunsaturated caps. In certain embodiments, a process for preparing anestolide base oil comprising providing at least one first fatty acidreactant and at least one second fatty acid reactant and a Lewis acidcan be conducted with feedstock comprising myristoleic, palmitoleic,oleic acids, or combinations thereof.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about70° C., about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C., about 55° C. to about 65°C., about 60° C. to about 70° C., about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C., about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place at a pressure of less than 5 torr or greater than 15 torrabs, and a temperature of about 50° C. to about 60° C., about 55° C. toabout 65° C., about 60° C. to about 70° C., about 65° C. to about 75°C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about70° C., about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C., about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C., about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Bi(OTf)₃, and at least a portion of the oligomerizing steptakes place at a pressure of less than 5 torr or greater than 15 torrabs, and a temperature of about 50° C. to about 60° C. about 55° C. toabout 65° C., about 60° C. to about 70° C. about 65° C. to about 75° C.,or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C. about 55° C. to about 65° C., about 60° C. to about70° C. about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, and at least a portion of the oligomerizing steptakes place at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C., about 55° C. to about 65°C. about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C. about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, and at least a portion of the oligomerizing steptakes place at a pressure of less than 5 torr or greater than 15 torrabs, and a temperature of about 50° C. to about 60° C. about 55° C. toabout 65° C., about 60° C. to about 70° C. about 65° C. to about 75° C.,or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about70° C. about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Cu(OTf)₂, at a pressure of less than 5 torr or greater than15 torr abs, and a temperature of about 50° C. to about 60° C., about55° C. to about 65° C. about 60° C. to about 70° C. about 65° C. toabout 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about70° C. about 65° C. to about 75° C., and about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, at a pressure of less than 5 torr or greater than15 torr abs, and a temperature of about 50° C. to about 60° C., about55° C. to about 65° C., about 60° C. to about 70° C. about 65° C. toabout 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C. about 55° C. to about 65° C., about 60° C. to about70° C. about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, and at least a portion of the oligomerizing steptakes place at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the process for preparing an estolide base oil is abatch, semi-continuous, or continuous process, wherein the Lewis acidcatalyst is Fe(OTf)₃, at least no portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of less than 5 torr or greater than 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

The present disclosure also provides an improved process foresterification to provide esters. In some embodiments, the process is abatch, semi-continuous, or continuous process.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about70° C. about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, and at least a portion of the oligomerizing steptakes place at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, and at least a portion of the oligomerizing steptakes place at a pressure of less than 5 torr or greater than 15 torrabs, and a temperature of about 50° C. to about 60° C. about 55° C. toabout 65° C., about 60° C. to about 70° C. about 65° C. to about 75° C.,or about 70° C. to about 80° C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, and at least a portion of the oligomerizing steptakes place in the presence of applied microwave radiation, at apressure of between 5 and 15 torr abs, and at a temperature of about 50°C. to about 60° C. about 55° C. to about 65° C. about 60° C. to about70° C. about 65° C. to about 75° C., or about 70° C. to about 80° C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof at a pressure of between 5 and 15 torr abs, and atemperature of about 50° C. to about 60° C., about 55° C. to about 65°C., about 60° C. to about 70° C. about 65° C. to about 75° C., or about70° C. to about 80° C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, or acombinations thereof, at least a portion of the oligomerizing step takesplace in the presence of applied microwave radiation, at a pressure ofless than 5 torr or greater than 15 torr abs, and a temperature of about50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. toabout 70° C. about 65° C. to about 75° C., or about 70° C. to about 80°C.

In some embodiments, the esterifying is catalyzed by Bi(OTf)₃, at apressure of less than 5 torr or greater than 15 torr abs, and atemperature of about 50° C. to about 60° C. about 55° C. to about 65° C.about 60° C. to about 70° C. about 65° C. to about 75° C., or about 70°C. to about 80° C. In certain embodiments, estolide base oil isesterified with at least one alcohol in the presence of anesterification catalyst, optionally in the presence of applied microwaveradiation.

In certain embodiments, a process for preparing an estolide base oil isprovided that comprises providing at least one fatty acid reactant, atleast one second fatty acid reactant and a Lewis acid catalysts, whereinthe at least one first fatty acid reactant is an unsaturated fatty acidor an oligomer of unsaturated fatty acids and/or the at least one secondfatty acid reactant is an unsaturated fatty acid or an oligomer ofunsaturated fatty acids, and the Lewis acid catalyst is a triflate. Incertain embodiments, the Lewis acid catalyst is selected from AgOTf,Cu(OTf)₂, Fe(OTf)₂, Fe(OTf)₃, NaOTf, LiOTf, Yb(OTf)₃, Y(OTf)₃, Zn(OTf)₂,Ni(OTf)₂, Bi(OTf)₃, La(OTf)₃, Sc(OTf)₃, and combinations thereof.

In certain embodiments, a process for preparing an estolide base oil isprovided that comprises providing at least one fatty acid reactant, atleast one second fatty acid reactant and a Lewis acid catalysts, whereinthe at least one first fatty acid reactant is an unsaturated fatty acidor an oligomer of unsaturated fatty acids and/or the at least one secondfatty acid reactant is an unsaturated fatty acid or an oligomer ofunsaturated fatty acids, and the Lewis acid catalyst is an ironcompound. In certain embodiments, the catalyst is a Lewis acid selectedfrom Fe(acac)₃, FeCl₃, Fe₂(SO₄)₃, Fe₂O₃, FeSO₄, and combinationsthereof. In certain embodiments, the process further includes use of aBronsted acid as a catalyst wherein the Bronsted acid is sulfamic acid,methylsulfamic acid or combinations thereof.

In certain embodiments, the process for preparing an estolide base oilis a continuous process, wherein the catalyst is a Lewis acid selectedfrom Fe(acac)₃, FeCl₃, Fe₂(SO₄)₃, Fe₂O₃, FeSO₄, and combinationsthereof, and the process optionally further includes use of a Bronstedacid as a catalyst wherein the Bronsted acid is sulfamic acid,methylsulfamic acid or combinations thereof.

In certain embodiments estolide compounds and compositions are producedby a process comprising

providing at least one first fatty acid reactant, at least one secondfatty acid reactant, and a Lewis acid catalyst; and

oligomerizing the at least one first fatty acid reactant with the atleast one second fatty acid reactant in the presence of the Lewis acidcatalyst to produce an estolide compound and/or estolide composition.

In certain embodiments, the at least one first fatty acid reactant isselected from one or more unsaturated fatty acids, one or moreunsaturated fatty acid oligomers, and combinations thereof. In someembodiments, the at least one second fatty acid reactant is selectedfrom saturated and unsaturated fatty acids, saturated and unsaturatedfatty acid oligomers, and combinations thereof.

Without being bound to any particular theory, in certain embodiments, itis believed that an estolide is formed when a Lewis acid catalyst isused to produce a carbocation at a site of unsaturation on either afirst or second fatty acid reactant, which is followed by nucleophilicattack on the carbocation by the carboxylic group of the other fattyacid. As noted above, in certain embodiments, suitable unsaturated fattyacids for preparing the estolides may include any mono- orpolyunsaturated fatty acid. For example, in some embodiments,monounsaturated fatty acids, along with a suitable catalyst, will form asingle carbocation for the addition of a second fatty acid (saturated orunsaturated), whereby a covalent bond between two fatty acid is formed.Suitable monounsaturated fatty acids may include, but are not limitedto, palmitoleic (16:1), vaccenic (18:1), oleic acid (18:1), eicosenoicacid (20:1), erucic acid (22:1), and nervonic acid (24:1). In addition,polyunsaturated fatty acids may be used to create estolides. Suitablepolyunsaturated fatty acids may include, but are not limited to,hexadecatrienoic acid (16:3), alpha-linolenic acid (18:3), stearidonicacid (18:4), eicosatrienoic acid (20:3), eicosatetraenoic acid (20:4),eicosapentaenoic acid (20:5), heneicosapentaenoic acid (21:5),docosapentaenoic acid (22:5), docosahexaenoic acid (22:6),tetracosapentaenoic acid (24:5), tetracosahexaenoic acid (24:6),linoleic acid (18:2), gamma-linoleic acid (18:3), eicosadienoic acid(20:2), dihomo-gamma-linolenic acid (20:3), arachidonic acid (20:4),docosadienoic acid (20:2), adrenic acid (22:4), docosapentaenoic acid(22:5), tetracosatetraenoic acid (22:4), tetracosapentaenoic acid(24:5), pinolenic acid (18:3), podocarpic acid (20:3), rumenic acid(18:2), alpha-calendic acid (18:3), beta-calendic acid (18:3), jacaricacid (18:3), alpha-eleostearic acid (18:3), beta-eleostearic (18:3),catalpic acid (18:3), punicic acid (18:3), rumelenic acid (18:3),alpha-parinaric acid (18:4), beta-parinaric acid (18:4), andbosseopentaenoic acid (20:5).

In certain embodiments, the process for preparing the estolide compoundsmay include the use of any natural or synthetic fatty acid source.However, it may be desirable to source the fatty acids from a renewablebiological feedstock. In some embodiments, suitable starting materialsof biological origin may include plant fats, plant oils, plant waxes,animal fats, animal oils, animal waxes, fish fats, fish oils, fishwaxes, algal oils and mixtures thereof. Other potential fatty acidsources may include waste and recycled food-grade fats and oils, fats,oils, and waxes obtained by genetic engineering, fossil fuel basedmaterials and other sources of the materials desired.

In certain embodiments, Lewis acid catalysts for preparing the estolidesmay include triflates (trifluormethanesulfonates) such as transitionmetal triflates and lanthanide triflates. Suitable triflates may includeAgOTf (silver triflate), Cu(OTf)₂ (copper triflate), NaOTf (sodiumtriflate), Fe(OTf)₂ (iron (II) triflate), Fe(OTf)₃ (iron (III)triflate), LiOTf (lithium triflate), Yb(OTf)₃ (ytterbium triflate),Y(OTf)₃ (yttrium triflate), Zn(OTf)₂ (zinc triflate), Ni(OTf)₂ (nickeltriflate), Bi(OTf)₃ (bismuth triflate), La(OTf)₃ (lanthanum triflate),Sc(OTf)₃ (scandium triflate), and combinations thereof. In someembodiments, the Lewis acid catalyst is Fe(OTf)₃. In some embodiments,the Lewis acid catalyst is Bi(OTf)₃.

In certain embodiments, Lewis acid catalysts may include metalcompounds, such as iron compounds, cobalt compounds, nickel compounds,and combinations thereof. In some embodiments, the metal compounds maybe selected from FeX_(n) (n=2, 3), Fe(CO)₅, Fe₃(CO)₁₂, Fe(CO)₃(ET),Fe(CO)₃(DE), Fe(DE)₂, CpFeX(CO)₂, [CpFe(CO)₂]₂, [Cp*Fe(CO)₂]₂,Fe(acac)₃, Fe(OAc)_(n) (n=2, 3), CoX₂, CO₂(CO)₈, Co(acac)_(n), (n=2, 3),Co(OAc)₂, CpCO(CO)₂, Cp*Co(CO)₂, NiX₂, Ni(CO)₄, Ni(DE)₂, Ni(acac)₂,Ni(OAc)₂, and combinations thereof, wherein X is selected from hydrogen,halogen, hydroxyl, cyano, alkoxy, carboxylato, and thiocyanato; whereinCp is a cyclopentadienyl group; acac is an acetylacetonato group; DE isselected from norbornadienyl, 1,5-cyclooctadienyl, and 1,5-hexadienyl;ET is selected from ethylenyl and cyclooctenyl; and OAc represents anacetate group. In some embodiments, the Lewis acid is an iron compound.In some embodiments, the Lewis acid is an iron compound selected fromFe(acac)₃, FeCl₃, Fe₂(SO₄)₃, Fe₂O₃, FeSO₄, and combinations thereof.

In some embodiments, the oligomerization process comprises use of one ormore of protic or aprotic catalysts.

In some embodiments, the oligomerization processes are aided by theapplication of electromagnetic energy. In certain embodiments, theelectromagnetic energy used to aid the oligomerization is microwaveelectromagnetic energy. In certain embodiments, for example, applicationof electromagnetic radiation may be applied to reduce the overallreaction time and improve the yield of estolide by conducting thereaction in a microwave reactor in the presence of an oligomerizationcatalyst. In some embodiments, oligomerizing the at least one firstfatty acid reactant with the at least one second fatty acid reactant isconducted in the presence of an oligomerization catalyst (e.g., a Lewisacid) and microwave radiation. In some embodiments, the oligomerizationis conducted in a microwave reactor with Bi(OTf)₃.

In some embodiments, the processes may further comprise the use of oneor more Bronsted acids. For example, in some embodiments, theoligomerizing step may further comprise the presence of a Bronsted acid.Exemplary Bronsted acids include, but are not limited to, hydrochloricacid, nitric acid, sulfamic acid, methylsulfamic acid, sulfuric acid,phosphoric acid, perchloric acid, triflic acid, p-toluenesulfonic acid(p-TsOH), and combinations thereof. In some embodiments, the Bronstedacid is selected from sulfamic acid, methylsulfamic acid, andcombinations thereof. In some embodiments, the Bronsted acid maycomprise cation exchange resins, acid exchange resins and/orsolid-supported acids. Such materials may include styrene-divinylbenzenecopolymer-based strong cation exchange resins such as Amberlyst® (Rohm &Haas; Philadelphia, Pa.), Dowex® (Dow; Midland, Mich.), CG resins fromResintech, Inc. (West Berlin, N.J.), and Lewatit resins such asMonoPlus™ S 100H from Sybron Chemicals Inc. (Birmingham, N.J.).Exemplary solid acid catalysts include cation exchange resins, such asAmberlyst® 15, Amberlyst® 35, Amberlite® 120, Dowex® Monosphere M-31,Dowex® Monosphere DR-2030, and acidic and acid-activated mesoporousmaterials and natural clays such a kaolinites, bentonites, attapulgites,montmorillonites, and zeolites. Examplery catalysts are also includedorganic acids supported on mesoporous materials derived frompolysaccharides and activated carobon, such as Starbon®—supportedsulphonic acid catalysts (University of York) like Starbon® 300,Starbon® 400, and Starbon® 800. Phosphoric acids on solid supports mayalso be suitable, such as phosphoric acid supported on silica (e.g.,SPA-2 catalysts sold by Sigma-Aldrich).

In certain embodiments, fluorinated sulfonic acid polymers may be usedas solid-acid catalysts for the processes described herein. These acidsare partially or totally fluorinated hydrocarbon polymers containingpendant sulfonic acid groups, which may be partially or totallyconverted to the salt form. Exemplary sulfonic acid polymers includeNafion® perfluorinated sulfonic acid polymers such as Nation® SAC-13(E.I. du Pont de Nemours and Company, Wilmington, Del.). In certainembodiments, the catalyst includes Nafion® Super Acid Catalyst, abead-form strongly acidic resin which is a copolymer oftetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene sulfonylfluoride, converted to either the proton (H⁺), or the metal salt form.

In some embodiments, depending on the nature of the catalyst and thereaction conditions, it may be desirable to carry out the process at acertain temperature and/or pressure. In some embodiments, for example,suitable temperatures for effecting oligomerization may includetemperatures greater than about 50° C., such as a range of about 50° C.to about 100° C. In some embodiments, the oligomerization is carried outat about 60° C. to about 80° C. In some embodiments, the oligomerizationis carried out, for at least a portion of the time, at about 50° C.,about 52° C., about 54° C., about 56° C., about 58° C., about 60° C.,about 62° C., about 64° C., about 66° C., about 68° C., about 70° C.,about 72° C., about 74° C., about 76° C., about 78° C., about 80° C.,about 82° C., about 84° C., about 86° C., about 88° C., about 90° C.,about 92° C., about 94° C., about 96° C., about 98° C., and about 100°C. In some embodiments, the oligomerization is carried out, for at leasta period of time, at a temperature of no greater than about 52° C.,about 54° C., about 56° C., about 58° C., about 60° C., about 62° C.,about 64° C., about 66° C., about 68° C., about 70° C., about 72° C.,about 74° C., about 76° C., about 78° C., about 80° C., about 82° C.,about 84° C., about 86° C., about 88° C., about 90° C., about 92° C.,about 94° C., about 96° C., about 98° C., or about 100° C.

In some embodiments, suitable oligomerization conditions may includereactions that are carried out at a pressure of less than 1 atm abs(absolute), such at less than about 250 torr abs, less than about 100torr abs, less than about 50 torr abs, or less than about 25 torr abs.In some embodiments, oligomerization is carried out at a pressure ofabout 1 torr abs to about 20 torr abs, or about 5 torr abs to about 15torr abs. In some embodiments, oligomerization, for at least a period oftime, is carried out at a pressure of greater than about 5, about 10,about 15, about 20, about 25, about 30, about 35, about 40, about 45,about 50, about 55, about 60, about 65, about 70, about 75, about 80,about 85, about 90, about 95, about 100, about 105, about 110, about115, about 120, about 125, about 130, about 135, about 140, about 145,about 150, about 155, about 160, about 165, about 170, about 175, about180, about 185, about 190, about 195, about 200, about 205, about 210,about 215, about 220, about 225, about 230, about 235, about 240, about245, and about 250 torrs abs. In some embodiments, oligomerization, forat least a period of time, is carried out at a pressure of less thanabout 5, about 10, about 15, about 20, about 25, about 30, about 35,about 40, about 45, about 50, about 55, about 60, about 65, about 70,about 75, about 80, about 85, about 90, about 95, about 100, about 105,about 110, about 115, about 120, about 125, about 130, about 135, about140, about 145, about 150, about 155, about 160, about 165, about 170,about 175, about 180, about 185, about 190, about 195, about 200, about205, about 210, about 215, about 220, about 225, about 230, about 235,about 240, about 245, or about 250 torrs abs. In some embodiments, theprocesses described herein further comprise the step of esterifying theresulting free acid estolide in the presence of at least oneesterification catalyst. Suitable esterification catalysts may includeone or more Lewis acids and/or Bronsted acids, including, for A example,AgOTf, Cu(OTf)₂, Fe(OTf)₂, Fe(OTf)₃, NaOTf, LiOTf, Yb(OTf)₃, Y(OTf)₃,Zn(OTf)₂, Ni(OTf)₂, Bi(OTf)₃, La(OTf)₃, Sc(OTf)₃, hydrochloric acid,nitric acid, sulfuric acid, phosphoric acid, perchloric acid, triflicacid, p-TsOH, and combinations thereof. In some embodiments, theesterification catalyst may comprise a strong Lewis acid such as BF₃etherate. In some embodiments, the Lewis acid of the oligomerizing stepand the esterification catalyst will be the same, such as Bi(OTf)₃. Insome embodiments, the esterification is conducted in the presence ofmicrowave radiation.

In some embodiments, the esterification catalyst may comprise a Lewisacid catalyst, example, at least one metal compound selected fromtitanium compounds, tin compounds, zirconium compounds, hafniumcompounds, and combinations thereof. In some embodiments, the Lewis acidesterification catalyst is at least one titanium compound selected fromTiCl₄, Ti(OCH₂CH₂CH₂CH₃)₄ (titanium (IV) butoxide), and combinationsthereof. In some embodiments, the Lewis acid esterification catalyst isat least one tin compound selected from Sn(O₂CCO₂) (tin (II) oxalate),SnO, SnCl₂, and combinations thereof. In some embodiments, the Lewisacid esterification catalyst is at least one zirconium compound selectedfrom ZrCl₄, ZrOCl₂, ZrO(NO₃)₂, ZrO(SO₄), ZrO(CH₃COO)₂, and combinationsthereof. In some embodiments, the Lewis acid esterification catalyst isat least one hafnium compound selected from HfCl₂, HfOCl₂, andcombinations thereof. Unless stated otherwise, all metal compounds andcatalysts discussed herein should be understood to include their hydrateand solvate forms. For example, in some embodiments, the Lewis acidesterification catalyst may be selected from ZrOCl₂.8H₂O andZrOCl₂.2THF, or HfOCl₂.2THF and HfOCl₂-8H₂O.

Also described herein is a process of producing a carboxylic acid ester,comprising:

providing at least one carboxylic acid reactant, at least one olefin,and a Bismuth catalyst; and reacting the at least one carboxylic acidreactant with the at least one olefin in the presence of the Bismuthcatalyst to produce a carboxylic acid ester.

In certain embodiments, the carboxylic acid reactant(s) may comprise analiphatic carboxylic acid, such as an optionally substituted fatty acidthat is branched or unbranched and saturated or unsaturated. It shouldbe understood that aliphatic carboxylic acids may include cyclic andacyclic carboxylic acids. Other examples of aliphatic carboxylic acidsmay include acetic acid, propionic acid, butyric acid, isobutyric acid,acrylic acid, methacrylic acid, and the like.

In some embodiments, the carboxylic acid reactant may comprise any ofthe fatty acid reactants previously described herein, such as fatty acidoligomers and free fatty acid estolides. In some embodiments, thecarboxylic acid reactant may comprise aromatic carboxylic acids such asbenzoic acid, anisic acid, phenylacetic acid, salicylic acid, o-toluicacid, phthalic acid, isophthalic acid, terephthalic acid, and the like.In some embodiments, the at least one olefin may be optionallysubstituted and branched or unbranched. Suitable olefins may includealiphatic olefins and aromatic olefins. Aliphatic olefins include cyclicand acyclic olefins. In some embodiments, aliphatic olefins may includeethylene, propylene, isopropylene, butene, pentene, hexene, heptene,octane, and the like. Examples of the aromatic olefins include styrene,divinylbenzene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylpyridine,and the like.

Examples of cyclic olefins include a monocyclic olefin, and a bridgedcyclic hydrocarbon represented by a bicyclo compound such as norborneneswhich have distortion in the cyclic structure. Examples of themonocyclic olefin include a cyclic olefin with 3-6 carbon atoms such ascyclopropene, cyclobutene, cyclopentene, methylcyclopentene, andcyclohexene. Substituents for the carboxylic acid reactants and olefinsmay include any substituent that are appropriate as substituents forestolide compounds.

In some embodiments, the processes described herein may comprise acontinuous flow process. The continuous flow processes may comprise theuse of an oligomerization catalyst. In some embodiments, the continuousflow processes comprise use of a Lewis acid catalyst. In someembodiments a continuous process for producing an estolide baseoilcomprises: providing at least one first fatty acid reactant, at leastone second fatty acid reactant, and an oligomerization catalyst; andcontinuously oligomerizing the at least one first fatty acid reactantwith the at least one second fatty acid reactant in the presence of theoligomerization catalyst to produce an estolide base oil.

Unless otherwise stated, it should be understood that suitablematerials, conditions, and compounds for practicing the continuousprocess may include the materials, conditions, and compounds, discussedherein for producing estolides, estolide base oils, and compositionscomprising estolides.

In some embodiments, at least one first fatty acid reactant and at leastone oligomerization catalyst are continuously provided to a region orlocation where the at least one fatty acid reactant reacts to formestolides and/or esters. In some embodiments, the at least oneoligomerization catalyst catalyzes the oligomerization and/oresterification. In some embodiments, a first fatty acid reactant and atleast one oligomerization catalyst are continuously provided atintervals, for example, at intervals of time including 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 50, and 60 minutes, and 2, 3, 4, 5,6, or 7 hours, or, for example, intervals measured by degree of reactioncompletion including 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, 90, and 95% completion.

In some embodiments, at least one first fatty acid reactant and at leastone second fatty acid reactant are continuously oligomerized in areactor. In some embodiments, exemplary reactors include single vesselswith a substantial degree of back-mixing, with or without mechanicalagitation, such that the dwell time within the vessel of an identifiedportion of entering material is more or less random (e.g., “continuousstir tank reactor”). In some embodiments, reactors or reaction vesselsmay optionally include a heater or heat source. In some embodiments, thereactors or reaction vessels may include, upon operation, a quantity ofliquid and a quantity of vapor. In some embodiments, the quantity ofliquid will contain a greater fraction of estolide(s) relative to fattyacid reactant than the fraction of estolide(s) relative to fatty acidreactant in the quantity of vapor. In certain embodiments, a point ofexit for vapor and/or a point of exit for liquid reactants and/orproducts will be provided.

In certain embodiments, reactor(s) may be a sequence(s) of back-mixedvessels, wherein the reaction mixture from one vessel constitutes thefeed for a further vessel. In some embodiments, there is a combinationof vessels and material is exchanged between them. In certainembodiments, the exchange of material between vessels in a combinationis sufficiently rapid that a main flow of material into and/or out ofthe combination of vessels does not prevent the combination from actingas a single fully-back-mixed or partially-back-mixed vessel. Otherembodiments may include horizontal or vertical vessels of large ratio oflength to cross-sectional linear dimension (i.e., pipes and columns)through which the reacting material flows and in which identifiedportions of the material pass any point along the length inapproximately the same order as at any other point (commonly known as“plug flow”).

In certain embodiments, the temperature of the reactor(s) and/orreaction vessels may be controlled. In some embodiments, the temperatureof the reactor(s) and/or reaction vessels can be controlled to providezones or regions of differing temperature. In some embodiments, heatenergy may be supplied along the length of the vessel(s) to conduct theoligomerization and/or to improve flow of material within the vessel(s)by decreasing the viscosity of reactants and/or products.

In certain embodiments, the reactor and/or reaction vessels may have thecharacter that material introduced in the reactor and/or reactionvessels will pass from a first region where introduced in the reactor toincreasing distal regions by flow and/or transport in a liquid and/orvapor state. In certain embodiments, the reactor and/or reaction vesselis a pipe or column optionally provided with one or more partialbarriers which allow passage of fluid in the desired directions. Incertain embodiments, the passage of fluid in directions other than thedesired direction can be prevented or lessened by one or more partialbarriers which allow passage of fluid in a desired direction, but whichlargely prevent back-flow of fluid.

In certain embodiments, combinations of back-mixed vessels and pipes orcolumns are used, optionally in sequence. In some embodiments, thereactor may comprise vessels incorporating large vertical surfaces, downwhich the reaction mixture flows and reacts. Vessels may, for example,in certain embodiments be designed to increase the available surfacearea relative to that available on flat or simple curved surfaces.

In certain embodiments, hybrid batch-continuous systems may be used,where at least a part of the process is carried out in each mode. Incertain embodiments, the feed material is prepared in batches and fedcontinuously to a continuous reactor, and/or the product of thecontinuous reactor is further processed as individual batches.

In certain embodiments, the process is conducted in a semi-continuousreactor wherein both periodical and continuous charging of the reactorwith reactants is combined with only periodic discharge of resultingproduct. For example, in certain embodiments of semi-continuousreactors, one or more initial reactants is charged in full, while asecond or further reactant is only supplied gradually until the one ormore initial reactants is exhausted. In other embodiments,semi-continuous reactors can comprise periodic discharge of the productor a mixture of product and reactants when a particular degree ofcompletion has been attained. For example, in certain embodiments, thedegree of completion for a semi-continuous reactor may be 10, 20, 30,40, 50, 60, 70, 80, 90, or 100%.

In certain embodiments, a continuous process is carried out in a tankreactor such as a continuous stirred tank reactor. FIG. 1 illustratesexemplary process system 100, which includes continuous stirred tankreactor 102 and separation unit 104. Reactor 102 may be equipped withpaddle stirrer 108 and, optionally, a heat source, which may or may notbe located within the reaction medium. The heat source may be aninternal replaceable heat source that comprises a non-fluid heatingmedia. By replaceable, it is meant that the heat source can be replacedwithout the need to shut down the equipment to remove if a heater burnsout. In some embodiments, for example, there can be an internal heaterlocated centrally to the reactor. In certain embodiments, the heatsource for reactor 102 may be in the form of an external jacket throughwhich hot oil, warm water, or steam which may or may not be saturated,may be used to heat the reactor vessel.

In some embodiments, continuous processes may be performed byintroducing one or more fatty acid reactants and an oligomerizationcatalyst into reactor 102 via inlet 106. Preparation of the desiredestolide oligomer may be controlled by, for example, catalyst content,residence time of the reactants, stir rate, temperature, pressure, or acombination thereof. By continuously providing reactants and catalyst toreactor 102, it may be possible to control the size of the oligomerproduct recovered from the reactor(s). In some embodiments, for example,by continuously providing catalyst and reactants, and decreasingresidence time, the oligomer products obtained will be smaller oligomers(e.g., estolides having a lower EN). Resulting oligomers can then beremoved from reactor 102 via outlet 132. Opening valve 116 and closingvalve 122 will allow for the transport of the oligomer product alongconduit 110 to a secondary site for storage or, optionally, furtherprocessing (e.g., esterification, catalyst removal or recovery, orcontinued oligomerization). If desired, opening valve 114 and closingvalve 116 will allow for the return of the oligomers and/or fatty acidsto reactor 102 via conduit 112 for further oligomerization. Accordingly,in certain embodiments the continuous process comprises oligomerizingthe reactants to form one or more first estolides. In some embodiments,at least a portion of the one or more first estolides is removed fromthe reactor. In certain embodiments, at least a portion of the one ormore first estolides is transferred back to the reactor, or to asecondary reactor, for continued oligomerization to provide one or moresecond estolides. In some embodiments, the one or more second estolideshave an EN that is greater than the EN of the one or more firstestolides.

As noted above, in certain embodiments, the size of the estolides may beincreased by increasing the residence time of the reactants in reactor102, or by removing and subsequently returning a portion of theoligomers to the reactor for further processing. In certain embodiments,the desired EN for the oligomers is achieved, opening valve 122 andclosing valve 116 allows for the transfer of the estolides to separationunit 104 via inlet 124. Separation unit 104 may be used to separate theestolides into two or more groups of varying size. Separation unit 104may implement any suitable separation technique, including distillation,phase separation, chromatography, membrane separation, affinityseparation, solvent extraction, or combinations thereof. As discussedfurther below with respect to FIG. 2, separation unit 104 may comprise astructure that is substantially similar to that of column reactor 200.Smaller oligomers (lower EN) may be transferred out of separation unit104 via outlet 120, while larger oligomers (larger EN) can be removedvia outlet 128. Thus, in some embodiments, the processes describedherein comprise transferring estolides from the reactor to a separationunit for separation into one or more estolide products. In turn, in someembodiments, the one or more estolide products can be transferred fromseparation unit 104 to one or more secondary reactors for furtherprocessing (e.g., esterification, oligomerization) or may be transferredto storage.

In certain embodiments, the reactor(s) or reaction vessels relate tocolumn reactors. Exemplary reactors for the processes described hereinmay also include column reactors (e.g., vertical column reactors), andplug flow reactors. While a number of column reactor configurations arepossible, vertical column reactor 200 is illustrated in FIG. 2. Andwhile the term “vertical” suggests substantially vertical, it isunderstood that there can be tilt or angle to the reactor.

FIG. 2 illustrates a column reactor useful for the processes forsynthesis of estolides according to certain embodiments. Column reactorscan either be in a single stage or multiple stage configuration. In someembodiments, the column reactor has multiple stages, such as reactor200, which has five stages (206, 212, 220, 232, and 236). If the reactoris co-current, the reaction mixture (reactants, oligomers, estolides)flow in one direction. In a counter-current reactor, the stages aredesigned to allow smaller materials (fatty acid reactants, smalleroligomers) to flow in a direction opposite to that of larger materials(larger oligomers/estolides). While the process of this reaction can beperformed in a single stage reactor, processes comprise the use of atleast two stages, and in some embodiments the process described hereincomprise the use of at least 3, 4, 5, 6, 7, 8, 9, or 10 stages. Incertain embodiments, the reactor has 5, 10, 15, 20, 25, 30, 35, 40, 45,50, 60, 70, 80, or 100 stages.

In some embodiments, the results of the processes described herein maybe improved by creating more efficient heat transfer from the column tothe reactant(s). In certain embodiments, this may be accomplished bydesigning the column wall configuration or by placing good heat transfermaterials such as glass beads of optimum surface to volume ratio in eachstage of the column. Alternatively, in certain embodiments, it may beaccomplished by providing a heat source located within the reactionmedium.

In certain embodiments, depending on the manner in which reactor 200 isused, stages 206, 212, 220, 232, and 236 may represent either a packedbed or a fractioning tray. A stage that is in the form of a packed bedmay or may not be composed of a catalyst. As noted above with respect toFIG. 1, in certain embodiments, separation unit 104 may comprise astructure that is substantially similar to that of reactor 200. Incertain embodiments, a separation unit 104 comprising a structure thatis substantially similar to that of reactor 200 may allow for moreefficient separation of the estolides prepared in reactor 102. Forexample, in some embodiments, the stages may comprise a packed bedcontaining a structured or random packing of rings and saddles, or acombination of packed beds and fractioning trays. Thus, in certainembodiments, the process comprises the use of both a continuous stirredtank reactor and a separation column. In certain embodiments, use of aconfiguration with both a continuous stirred tank reactor and aseparation column may be desirable in circumstances where theoligomerization catalyst is more easily handled in a tank reactor.

In certain embodiments, oligomerization may take place in the columnreactor itself. In certain embodiments, catalyst will be fed into thereactor simultaneously with the fatty acid or oligomer feed stream. Incertain embodiments, the one or more catalysts present in the reactorwill be present in the form of one or more packed beds. In certainembodiments, one or more catalysts will be fed into a reactor before thefatty acid or oligomer feed enters the reactor. In certain embodiments,the one or more catalysts will be fed into a reactor after the fattyacid or oligomer feed enters the reactor. In certain embodiments, thefatty acid and/or oligomer feed streams may be introduced into a reactorand/or into reaction vessels at or near the top, at or near the bottom,or at any other stage within the reactor and/or reaction vessels. Incertain embodiments, the one or more catalysts may be introduced into areactor and/or into reaction vessels at or near the top, at or near thebottom, or at any other stage within the reactor and/or reactionvessels.

In certain embodiments, the process is a counter-current process asdescribed with reference to FIG. 2. In certain embodiments, anoligomerization catalyst, such as a solid support catalyst, may bepositioned in reaction stage 212, and optionally in one or more ofstages 206, 220, 232, and 236. For example, in certain embodiments stage212 may represent a packed bed structure with one or more theoreticaltrays that comprises the catalyst. One or more fatty acid reactants arethen introduced to reaction stage 212 via conduit 210. Asoligomerization proceeds in stage 212, the process stream of reactantsand/or oligomerized products passes down through the stages. The stagesare designed such that the reaction mixture flows downwardly whilereactants and smaller oligomers are allowed to flow upwardly back tostage 212 or up to 206. While temperature may be uniform throughout thecolumn, varying the temperature at different stages may allow theoperator to control the oligomerization process and isolate estolides ofa specific size at each stage. For example, by defining a temperatureand pressure at stage 232, all reactants or oligomers that would be avapor at that condition will vaporize and flow upward through stage 220thereby leaving only compounds that are liquid at the definedconditions. Reactants and initial oligomerization products within thereactor may flow down into one or more stages, such as stages 220 and232. By operating stages 220 and 232 at temperatures that are greaterthan stage 212, it may be possible to isolate estolide oligomers of aspecific size, while forcing unreacted reactants and smaller oligomersback up into stage 212 for continued oligomerization. For example, incertain embodiments, a tray design for stages 220 and 232 allows for thecollection of larger estolide products. Perforations in the tray designof barrier 220 (e.g., bubble cap design) would allow for the passage ofreactants and smaller oligomers back up into stage 220 from stage 232and, depending on the temperature of that stage, further passage intothe packed bed of stage 212 for continued oligomerization. Thus, in someembodiments, the process described herein comprises oligomerizing atleast one fatty acid reactant in a first reaction stage to provide aninitial oligomerized product. In certain embodiments, at least a portionof the initial oligomerized product is transferred to at least onesecond reaction stage, wherein the initial oligomerized product isseparated into one or more first estolides and one or more secondestolides. In certain embodiments, the one or more second estolides willbe larger than the one or more first estolides, wherein the one or moresecond estolides have an EN that is greater than the one or more firstestolides. In certain embodiments, at least a portion of the one or morefirst estolides are returned to the first reaction stage for continuedoligomerization.

By continuously providing reactor 200 with fatty acid reactants andcatalyst (if catalyst is not already present within the reactor in theform of a packed bed), it is possible, in certain embodiments, tostrictly control the size and rate at which the estolide oligomers areformed. In certain embodiments, the overall conversion to oligomers andextent of oligomerization within the reactor may be controlled byadjusting the number of actual or theoretical trays within the reactor,the temperature and pressure at each stage, the amount of catalysteither fed at each stage or already present in the reactor in the formof a packed bed, and/or the amount of reactants fed at each stage. Incertain embodiments, as estolide sizes are increased, it may be possibleto separate the products by controlling the temperature and/or pressureof each stage, as larger estolides typically exhibit higher boilingpoints. In certain embodiments, by controlling an increase intemperature at each successive stage (e.g., the temperature increases ingoing from 206 to 212, from 212 to 230, from 230 to 232, and from 232 to236), larger estolide oligomers (higher EN) may be allowed to passthrough further successive stages than smaller oligomers, which may beretained at certain stages and/or returned to earlier stages (e.g.,stage 212). Thus, in certain embodiments, it may be possible to isolateestolides of specific sizes. In certain embodiments, the reactor may bedesigned to produce oligomers of a specific oligomer length which arecollected at various stages. For example, stage 220 may be designed tocollect medium size oligomers while stage 232 may be designed to collectlarger size oligomers (higher EN). In certain embodiments, one or moreconduits may be provided to transfer larger size oligomers from areactor and/or reaction vessel. For example, a conduit tied into stage232 may be used to transfer larger size oligomers from the reactorillustrated in FIG. 2. In certain embodiments, products and/or reactantstransferred from a reactor and/or reaction vessel can be subjected tofurther processing or can be stored for a period of time.

In certain embodiments, the average estolide size can be increased byincreasing the average EN of the estolide product. In some embodiments,the average EN at a given stage may be controlled by increasing thenumber of theoretical trays, including where the stage comprises or isin the form of a packed bed catalyst. In some embodiments, it may bepossible to increase oligomer size in one or more of the subsequentstages by also providing oligomerization catalyst in one or more ofstages 212, 220, 232, and 236. In certain embodiments, providingoligomerization catalyst in earlier stages may be accomplished by eitheradding more catalyst as a feed to one or more of these stages or byproviding catalyst in a packed bed design for one or more stages. Incertain embodiments, it may be possible to increase conversion ofreactants to estolides and increase estolide size (higher EN) within thereactor or reaction vessels by including one or more pump-arounds wherematerial within the reactor or reaction vessels is removed from onestage and pumped back up to a higher stage in the reactor and allowed topass back through the stages (e.g., material removed via conduit 238 isreintroduced into the reactor via conduit 210).

In certain embodiments, the process may be operated at less than oneatmosphere pressure. In some embodiments, application of sub-atmosphericpressure may facilitate removal of smaller oligomers and reactants fromlower reaction stages, as well as the removal of any volatile impuritiesthat may be present. Suitable temperatures and pressures may includethose previously discussed herein.

In certain embodiments, the conversion from reactants to oligomers maytake place in a “plug flow” reactor. In some embodiments, a plug flowreactor may be packed with one or more catalyst or the one or morecatalyst may enter the reactor with reactants introduced into thereactor. In certain embodiments, the feed to the reactor may becontinuous. In certain embodiments, conversion of reactants to oligomerproduct depends on residence time within the reactor. In certainembodiments, residence time within the reactor is a function of reactorlength. In certain embodiments, therefore, the extent of oligomerizationand/or EN of products can be affected by selection of the one or morecatalyst, the amount of catalyst (catalyst loading), the volumetric flowrate of the feed, the length of the reactor, the pressure, thetemperature(s) within the reactor, or combinations thereof.

In certain embodiments, suitable oligomerization catalysts may includeLewis acids, Bronsted acids, or combinations thereof, such as thosepreviously described herein. In certain embodiments, certain catalysts,such as Lewis acids and/or solid-supported Bronsted acids, may bedesirable for the continuous processes described herein. In certainembodiments, catalysts such as Fe(OTf)₃ and Bi(OTf)₃ may be recoveredand reused, including, for example, in subsequent oligomerizationprocesses. In certain embodiments, montmorillonite and/or zeolitecatalysts may be recovered for reuse. In certain embodiments,oligomerization catalysts such as Amberlyst and Dowex may used bypositioning the solid support in one or more stages of a reactor and/orreaction vessel.

The present disclosure further relates to methods of making estolidesaccording to Formula I, II, and III. By way of example, the reaction ofan unsaturated fatty acid with an organic acid and the esterification ofthe resulting free acid estolide are illustrated and discussed in thefollowing Schemes I and II. The present disclosure further relates tocatalysts used in methods of making estolides according to Formula I,II, and TR. The particular structural formulas used to illustrate thereactions correspond to those for synthesis of compounds according toFormula I and III; however, the methods apply equally to the synthesisof compounds according to Formula II, with use of compounds havingstructure corresponding to R₃ and R₄ with a reactive site ofunsaturation.

As illustrated below, compound 100 represents an unsaturated fatty acidthat may serve as the basis for preparing the estolide compounds andcompositions comprising estolide compounds.

In Scheme 1, wherein x is, independently for each occurrence, an integerselected from 0 to 20, y is, independently for each occurrence, aninteger selected from 0 to 20, and n is an integer greater than or equalto 1, unsaturated fatty acid 100 may be combined with compound 102 and aLewis acid to form free acid estolide 104. In certain embodiments, it isnot necessary to include compound 102, as unsaturated fatty acid 100 maybe exposed alone to Lewis acid conditions to form free acid estolide104, wherein R₁ would represent an unsaturated alkyl group. If compound102 is included in the reaction, R₁ may represent one or more optionallysubstituted alkyl residues that are saturated or unsaturated andbranched or unbranched. In certain embodiments, any suitable Lewis acidmay be implemented to catalyze the formation of free acid estolide 104,including but not limited to triflates, iron compounds, cobaltcompounds, nickel compounds, or combinations thereof. In certainembodiments, other catalysts may be used to catalyze the formation offree acid estolide 102. In certain embodiments, Bronsted acids, inaddition to the Lewis acid, or in the alternative to the Lewis acid maybe a catalyst. In some embodiments, Bronsted acid catalysts includehomogenous acids and/or strong acids like hydrochloric acid, sulfuricacid, perchloric acid, nitric acid, triflic acid, and the like may beused in estolide synthesis. In some embodiments, solid-supported acidcatalysts such as Amberlyst®, Dowex®, and Nafion® may also be used.

Similarly, in Scheme 2, wherein x is, independently for each occurrence,an integer selected from 0 to 20, y is, independently for eachoccurrence, an integer selected from 0 to 20, and n is an integergreater than or equal to 1, free acid estolide 104 may be esterified byany suitable procedure known to those of skilled in the art, such asLewis acid-catalyzed reduction with alcohol 202, to yield esterifiedestolide 204. Exemplary methods may include the use of strong Lewis acidcatalysts such as BF₃. Other methods may include the use of triflates,titanium compounds, tin compounds, zirconium compounds, hafniumcompounds, or combinations thereof.

As discussed above, in certain embodiments, the estolides describedherein may have improved properties which render them useful as basestocks for biodegradable lubricant applications. Such applications mayinclude, without limitation, crankcase oils, gearbox oils, hydraulicfluids, drilling fluids, dielectric fluids, greases two-cycle engineoils, greases, dielectric fluids, and the like. Other suitable uses mayinclude marine applications, where biodegradability and toxicity are ofconcern. In certain embodiments, the nontoxic nature certain estolidesdescribed herein may also make them suitable for use as lubricants inthe cosmetic and food industries.

In certain embodiments, estolide compounds may meet or exceed one ormore of the specifications for certain end-use applications, without theneed for conventional additives. For example, in certain instances,high-viscosity lubricants, such as those exhibiting a kinematicviscosity of greater than about 120 cSt at 40° C., or even greater thanabout 200 cSt at 40° C., may be desirable for particular applicationssuch as gearbox or wind turbine lubricants. Prior-known lubricants withsuch properties typically also demonstrate an increase in pour point asviscosity increases, such that prior lubricants may not be suitable forsuch applications in colder environments. However, in certainembodiments, the counterintuitive properties of certain compoundsdescribed herein (e.g., increased EN provides estolides with higherviscosities while retaining, or even decreasing, the oil's pour point)may make higher-viscosity estolides particularly suitable for suchspecialized applications.

Similarly, the use of prior-known lubricants in colder environments maygenerally result in an unwanted increase in a lubricant's viscosity.Thus, depending on the application, it may be desirable to uselower-viscosity oils at lower temperatures. In certain circumstances,low-viscosity oils may include those exhibiting a viscosity of lowerthan about 50 cSt at 40° C., or even about 40 cSt at 40° C. Accordingly,in certain embodiments, the low-viscosity estolides described herein mayprovide end users with a suitable alternative to high-viscositylubricants for operation at lower temperatures.

In some embodiments, it may be desirable to prepare lubricantcompositions comprising an estolide base stock. For example, in certainembodiments, the estolides described herein may be blended with one ormore additives selected from polyalphaolefins, synthetic esters,polyalkylene glycols, mineral oils (Groups I, II, and III), pour pointdepressants, viscosity modifiers, anti-corrosives, antiwear agents,detergents, dispersants, colorants, antifoaming agents, anddemulsifiers. In addition, or in the alternative, in certainembodiments, the estolides described herein may be co-blended with oneor more synthetic or petroleum-based oils to achieve the desiredviscosity and/or pour point profiles. In certain embodiments, certainestolides described herein also mix well with gasoline, so that they maybe useful as fuel components or additives.

In all of the foregoing examples, the compounds described may be usefulalone, as mixtures, or in combination with other compounds,compositions, and/or materials.

Methods for obtaining the novel compounds described herein will beapparent to those of ordinary skill in the art, suitable proceduresbeing described, for example, in the examples below, and in thereferences cited herein.

EXAMPLES Analytics

Nuclear Magnetic Resonance: NMR spectra were collected using a BrukerAvance 500 spectrometer with an absolute frequency of 500.113 MHz at 300K using CDCl₃ as the solvent. Chemical shifts were reported as parts permillion from tetramethylsilane. The formation of a secondary ester linkbetween fatty acids, indicating the formation of estolide, was verifiedwith ¹H NMR by a peak at about 4.84 ppm.

Estolide Number (EN): The EN was measured by GC analysis. It should beunderstood that the EN of a composition specifically refers to ENcharacteristics of any estolide compounds present in the composition.Accordingly, an estolide composition having a particular EN may alsocomprise other components, such as natural or synthetic additives, othernon-estolide base oils, fatty acid esters, e.g., triglycerides, and/orfatty acids, but the EN as used herein, unless otherwise indicated,refers to the value for the estolide fraction of the estolidecomposition.

Iodine Value (IV): The iodine value is a measure of the degree of totalunsaturation of an oil. IV is expressed in terms of centigrams of iodineabsorbed per gram of oil sample. Therefore, the higher the iodine valueof an oil the higher the level of unsaturation is of that oil. The IVmay be measured and/or estimated by GC analysis. Where a compositionincludes unsaturated compounds other than estolides as set forth inFormula I, II, and III, the estolides can be separated from otherunsaturated compounds present in the composition prior to measuring theiodine value of the constituent estolides. For example, if a compositionincludes unsaturated fatty acids or triglycerides comprising unsaturatedfatty acids, these can be separated from the estolides present in thecomposition prior to measuring the iodine value for the one or moreestolides.

Acid Value: The acid value is a measure of the total acid present in anoil. Acid value may be determined by any suitable titration method knownto those of ordinary skill in the art. For example, acid values may bedetermined by the amount of KOH that is required to neutralize a givensample of oil, and thus may be expressed in terms of mg KOH/g of oil.

Gas Chromatography (GC): GC analysis was performed to evaluate theestolide number (EN) and iodine value (IV) of the estolides. Thisanalysis was performed using an Agilent 6890N series gas chromatographequipped with a flame-ionization detector and an autosampler/injectoralong with an SP-2380 30 m×0.25 mm i.d. column.

The parameters of the analysis were as follows: column flow at 1.0mL/min with a helium head pressure of 14.99 psi; split ratio of 50:1;programmed ramp of 120-135° C. at 20° C./min, 135-265° C. at 7° C./min,hold for 5 min at 265° C.; injector and detector temperatures set at250° C.

Measuring EN and IV by GC: To perform these analyses, the fatty acidcomponents of an estolide sample were reacted with MeOH to form fattyacid methyl esters by a method that left behind a hydroxy group at siteswhere estolide links were once present. Standards of fatty acid methylesters were first analyzed to establish elution times.

Sample Preparation: To prepare the samples, 10 mg of estolide wascombined with 0.5 mL of 0.5M KOH/MeOH in a vial and heated at 100° C.for 1 hour. This was followed by the addition of 1.5 mL of 1.0 MH₂SO₄/MeOH and heated at 100° C. for 15 minutes and then allowed to coolto room temperature. One (1) mL of H₂O and 1 mL of hexane were thenadded to the vial and the resulting liquid phases were mixed thoroughly.The layers were then allowed to phase separate for 1 minute. The bottomH₂O layer was removed and discarded. A small amount of drying agent(Na₂SO₄ anhydrous) was then added to the organic layer after which theorganic layer was then transferred to a 2 mL crimp cap vial andanalyzed.

EN Calculation: The EN is measured as the percent hydroxy fatty acidsdivided by the percent non-hydroxy fatty acids. As an example, a dimerestolide would result in half of the fatty acids containing a hydroxyfunctional group, with the other half lacking a hydroxyl functionalgroup. Therefore, the EN would be 50% hydroxy fatty acids divided by 50%non-hydroxy fatty acids, resulting in an EN value of 1 that correspondsto the single estolide link between the capping fatty acid and basefatty acid of the dimer.

IV Calculation: The iodine value is estimated by the following equationbased on ASTM Method D97 (ASTM International, Conshohocken, Pa.):

${IV} = {{\Sigma 100} \times \frac{A_{f} \times {MW}_{I} \times d\; b}{{MW}_{f}}}$

-   -   A_(f)=fraction of fatty compound in the sample    -   MW₁=253.81, atomic weight of two iodine atoms added to a double        bond    -   db=number of double bonds on the fatty compound    -   MW_(f)=molecular weight of the fatty compound

Other Measurements: Except as otherwise described, pour point ismeasured by ASTM Method D97-96a, cloud point is measured by ASTM MethodD2500, viscosity/kinematic viscosity is measured by ASTM Method D445-97,viscosity index is measured by ASTM Method D2270-93 (Reapprovd 1998),specific gravity is measured by ASTM Method D4052, flash point ismeasured by ASTM Method D92, evaporative loss is measured by ASTM MethodD5800, vapor pressure is measured by ASTM Method D5191, and acuteaqueous toxicity is measured by Organization of Economic Cooperation andDevelopment (OECD) 203.

HPLC Analysis of Estolide Products: To analyze the % formation ofestolides from the processes described herein, HPLC may be used todetermine the AUC (area under curve) for the estolide products.

Equipment: HPLC with a Thermo Separations Spectra System AS 1000autosampler/injector (Fremont, Calif.) and a P2000 binary gradient pumpfrom Thermo Separation Products (Fremont, Calif.) coupled with anAlltech 500 ELSD evaporative light scattering detector (AlltechAssociates, Deerfield, Ill.). Reverse-phase analysis performed using aDynamax C-8 column (25 cm×4.6 mm i.d., 8 μm particle size, 60 Å poresize) from Agilent (Harbor City, Calif., part # r00083301c).

Parameters for Analysis: Run time: 16 minutes. Mobile phase: gradientelution at a flow rate of 1 mL/min; 0-4 minutes, 80% acetonitrile, 20%acetone; 6-10 minutes, 100% acetone; 11-16 minutes, 80% acetonitrile,20% acetone. The ELSD drift tube is set to 50° C. with the nebulizer setat 30 psi N₂, providing a flow rate of 2.0 standard liters per minute(SLPM). Full loop injection: 20 μL.

Sample Preparation: Take a few drops of estolide sample and mix it withabout 2-3 mL of hexane along with some pH 5 buffer (sodium phosphate,500 g per 4 L) and thoroughly mix it. Remove the pH 5 buffer. Dry thesample with sodium sulfate. Take a few drops of the dried sample (amountdepends on response of detector) and add it to a vial along with 1.75 mLof hexane. Sample is then ready for HPLC analysis.

Analysis: Elution times: Estolides, 10.3 to 13.9 min; Oleic Acid, 5.5min. ¹H NMR is used to verify the presence of estolide by a peak at 4.84ppm.

Example 1

The acid catalyst reaction was conducted in a 50 gallon PfaudlerRT-Series glass-lined reactor. Oleic acid (65 Kg, OL 700, Twin Rivers)was added to the reactor with 70% perchloric acid (992.3 mL, AldrichCat#244252) and heated to 60° C. in vacuo (10 torr abs) for 24 hrs whilecontinuously being agitated. After 24 hours the vacuum was released.2-Ethylhexanol (29.97 Kg) was then added to the reactor and the vacuumwas restored. The reaction was allowed to continue under the sameconditions (60° C., 10 torr abs) for 4 more hours. At which time, KOH(645.58 g) was dissolved in 90% ethanol/water (5000 mL, 90% EtOH byvolume) and added to the reactor to quench the acid. The solution wasthen allowed to cool for approximately 30 minutes. The contents of thereactor were then pumped through a 1 micron (p.) filter into anaccumulator to filter out the salts. Water was then added to theaccumulator to wash the oil. The two liquid phases were thoroughly mixedtogether for approximately 1 hour. The solution was then allowed tophase separate for approximately 30 minutes. The water layer was drainedand disposed of. The organic layer was again pumped through a 1μ filterback into the reactor. The reactor was heated to 60° C. in vacuo (10torr abs) until all ethanol and water ceased to distill from solution.The reactor was then heated to 100° C. in vacuo (10 torr abs) and thattemperature was maintained until the 2-ethylhexanol ceased to distillfrom solution. The remaining material was then distilled using a Myers15 Centrifugal Distillation still at 200° C. under an absolute pressureof approximately 12 microns (0.012 torr) to remove all monoestermaterial leaving behind estolides.

Example 2

Bronsted and Lewis acid catalysts were tested for their ability tooligomerize fatty acid reactants into estolide products. In a glassvessel, oleic acid (1.0 equiv, 2.0 g, OL 700, Twin Rivers) was addedwith the catalyst under continuous stirring. The crude reaction productwas then filtered and subjected to NMR analysis to confirm the formationof the estolide product. HPLC analysis was then used to determine theoverall yield of the estolide product. Results for each of the catalystsare provided in Table 1 below:

TABLE 1 Temp Catalyst Loading/Equiv. (° C.) Time (hrs) Yield (%)Amberlyst BD20   45 wt. % 140 18 20.3 Amberlyst 15   45 wt. % 80 18 45.2Amberlyst 35   45 wt. % 80 18 37.6 Fe(OTf)₃ 0.05 eq. 60 18 56.1 Bi(OTf)₃0.05 eq. 60 18 56.0 Dowex Monosphere   5 wt. % 110 12 17.2 DR-2030Nafion SAC-13   45 wt. % 110 16 16.4 AgOTf 0.05 eq. 110 16 18.2Montmorillonite K10 30% 110 14-18 22.8 Zn(OTf)₂ 0.05 eq. 140 18 16.0Fe₂O₃ 0.05 eq. 60 18 53.8 TfOH 0.15 eq. Fe₂(SO₄)₃ 0.05 eq. 110 18 9.5Fe₂(SO₄)₃ 0.05 eq. 60 18 49.8 TfOH 0.15 eq. FeCl₃ 0.05 eq. 60 18 48.8TfOH 0.15 eq. FePO₄•xH₂O 0.05 eq. 110 18 19.3 TfOH 0.15 eq. FeCl₃ 0.05eq. 80 18 47.3 AgOTf 0.15 eq. Cu(OTf)₂ 0.05 eq. 60 12 31.1 FeSO₄ 0.05eq. 140 12 9.3 Ammonium persulfate 0.50 eq.

Example 3

The ability to recover catalyst from catalytic reaction(s) set forth inExample 2 was tested. After the reaction was complete, the crude,unfiltered reaction mixture was cooled and subjected to workupconditions that allowed for recovery and reuse of the catalyst. Resultsare set forth in Table 2.

TABLE 2 Catalyst Conditions % Recovery Fe(OTf)₃ Cooled reaction mixturewas washed >90% 3X with cold water. Combined aqueous phase was heatedand dried under vacuum. Bi(OTf)₃ Hexanes are added to the cooled —reaction mixture to precipitate the catalyst, which is filtered andisolated.

Example 4

Catalysts recovered in Example 3 are recycled and tested for theirability to again convert fatty acid reactants into estolide products.Reaction conditions are substantially similar to those set forth inExample 2. The crude reaction products are then filtered and subjectedto NMR analysis to confirm the formation of the estolide product. HPLCanalysis is then used to determine the overall yield of the estolideproduct.

Example 5

Lewis acid catalysts were tested for their ability to esterify the freeacid estolide product of Example 1 with 2-ethylhexanol (2-EH). In aglass vessel under N₂ equipped with condenser, water separator, and stirbar, the estolide product of Example 1 (1.0 equiv.) was added with 2-EH(4.0 equiv) and the catalyst under continuous stirring. The reactionmixture was heated under continuous stirring, and water is removed fromthe water separator as needed. The crude reaction product was thendistilled under vacuum at 100° C. to remove any unreacted alcohol. Thereaction product was then filtered and subjected to NMR analysis toconfirm the formation of the estolide product. HPLC analysis is used todetermine that overall yield of the esterified product. Reactionconditions for each catalyst is are provided in Table 3 below:

TABLE 3 Catalyst Loading/Equiv. Temp (° C.) Time (hrs) Amberlyst 15 6.7wt. % 120 3 Amberlyst 35 6.7 wt. % 120 3 Fe(OTf)₃ 0.05 eq. 120 3Bi(OTf)₃ 0.05 eq. 120 3 Dowex Monosphere 6.7 wt. % 120 3 DR-2030 Dowex50WX8 (mesh 6.7 wt. % 120 3 50-100) Dowex 50WX8 (mesh 6.7 wt. % 120 3200-400) Nafion SAC-13 6.7 wt. % 120 3 Nafion NR40 6.7 wt. % 120 3 AgOTf0.05 eq. 120 3 Montmorillonite K10 6.7 wt. % 120 17 Zn(OTf)₂ 0.05 eq.120 3 Zeolite (75% ZSM- 6.7 wt. % 120 16 5/25% Al₂O₃), Non- calcinatedZeolite (75% ZSM- 6.7 wt. % 120 16 5/25% Al₂O₃), Calcinated ZeoliteZSM-5, 18.2% 6.7 wt. % 120 3 P₂O₅ NexCat (ZnO—La₂O₃) 6.7 wt. % 120 16Starbon 300 6.7 wt. % 120 3 Methylsulfamic acid 0.05 eq. 120 3Perchloric acid 0.05 eq. 120 3 Phosphoric acid 0.05 eq. 120 3 Cu(OTf)₂0.05 eq. 120 3 SPA-2 6.7 wt. % 120 3 Ti(OCH₂CH₂CH₂CH₃)₄ 0.03 eq. 80 16120 16 140 16 120 17 120 6 140 6 Sn(O₂CCO₂) 0.03 eq. 80 16 120 16 140 16120 17 120 6 140 6 ZrOCl₂•8H₂O 0.03 eq. 80 16 120 16 140 16 120 6 140 6Potassium Bisulfate 0.07 eq. 120 17

Example 6

Catalyst recovery for the Sn(O₂CCO₂) reactions set forth in Example 5 istested. Upon removal of the excess alcohol, the Sn(O₂CCO₂) precipitatesfrom solution. The precipitated catalysts is then filtered and dried.The activity of the recovered catalyst is then tested by subjecting itto a synthetic procedure substantially similar to that set forth inExample 5.

Example 7

In a Biotage Initiator microwave reactor (100 watts) was placed amicrowave reaction vial equipped with a magnetic stir bar, and oleicacid (1.0 equiv, OL 700, Twin Rivers) was added with the desired Lewisacid catalyst. Under continuous stirring, the reaction mixture washeated for 20 min in the microwave reactor. The crude reaction mixturewas then cooled and filtered. HPLC analysis was then used to determinethat overall yield of the estolide product. Results for each of thecatalysts are provided below in Table 4:

TABLE 4 Catalyst Loading/Equiv. Temp (° C.) Yield (%) Fe(OTf)₃ 0.05equiv. 40 13.0 60 41.1 80 39.2 100 31.0 Bi(OTf)₃ 0.05 equiv. 40 2.8 6033.6 80 49.4 100 27.7

Example 8

In a Biotage Initiator microwave reactor (100 watts) was placed amicrowave reaction vial equipped with a magnetic stir bar and theestolide product of Example 1 (1.0 equiv), Bi(OTf)₃ (0.1 equiv), and2-EH (10 equiv). With continuous stirring, the reaction mixture washeated to 150° C. for 20 min in the microwave reactor. The crudereaction mixture was then cooled and filtered. HPLC analysis of thereaction mixture indicated a >90% yield of the esterified estolide.

Example 9

Estolides will be prepared according to the method set forth in Examples1 and 5, except the 2-ethylhexanol esterifying alcohol is replaced withvarious other alcohols, including those identified below in Table 7:

TABLE 7 Alcohol Structure Jarcol ™ I-18CG iso-octadecanol Jarcol ™ I-122-butyloctanol Jarcol ™ I-20 2-octyldodecanol Jarcol ™ I-162-hexyldecanol Jarcol ™ 85BJ cis-9-octadecen-1-ol Fineoxocol ® 180

Jarcol ™ I-18T 2-octyldecanol

Example 10

Estolides to be prepared according to the method set forth in Examples 1and 5, except the 2-ethylhexanol esterifying alcohol will be replacedwith various alcohols, including those set forth below in Table 8, whichmay be saturated or unsaturated and unbranched or substituted with oneor more alkyl groups selected from methyl, ethyl, propyl, isopropyl,butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl,hexyl, isohexyl, and the like, to form a branched or unbranched residueat the R₂ position:

TABLE 8 Alcohol R₂ Substituents C₁ alkanol methyl C₂ alkanol ethyl C₃alkanol n-propyl, isopropyl C₄ alkanol n-butyl, isobutyl, sec-butyl C₅alkanol n-pentyl, isopentyl neopentyl C₆ alkanol n-hexyl, 2-methylpentyl, 3- methyl pentyl, 2,2-dimethyl butyl, 2,3-dimethyl butyl C₇alkanol n-heptyl and other structural isomers C₈ alkanol n-octyl andother structural isomers C₉ alkanol n-nonyl and other structural isomersC₁₀ alkanol n-decanyl and other structural isomers C₁₁ alkanoln-undecanyl and other structural isomers C₁₂ alkanol n-dodecanyl andother structural isomers C₁₃ alkanol n-tridecanyl and other structuralisomers C₁₄ alkanol n-tetradecanyl and other structural isomers C₁₅alkanol n-pentadecanyl and other structural isomers C₁₆ alkanoln-hexadecanyl and other structural isomers C₁₇ alkanol n-heptadecanyland other structural isomers C₁₈ alkanol n-octadecanyl and otherstructural isomers C₁₉ alkanol n-nonadecanyl and other structuralisomers C₂₀ alkanol n-icosanyl and other structural isomers C₂₁ alkanoln-heneicosanyl and other structural isomers C₂₂ alkanol n-docosanyl andother structural isomers

Example 11

“Ready” and “ultimate” biodegradability of the estolide produced in Ex.1 was tested according to standard OECD procedures. Results of the OECDbiodegradability studies are set forth below in Table 9:

TABLE 9 301D 28-Day 302D Assay (% degraded) (% degraded) Canola Oil 86.978.9 Ex. 1 64 70.9 Base Stock

Example 12

The Ex. 1 estolide base stock was tested under OECD 203 for AcuteAquatic Toxicity. The tests showed that the estolides are nontoxic, asno deaths were reported for concentration ranges of 5,000 mg/L and50,000 mg/L.

1-55. (canceled)
 56. A continuous process of producing an estolide baseoil comprising: continuously providing at least one first fatty acidreactant, at least one second fatty acid reactant, and anoligomerization catalyst; and continuously oligomerizing the at leastone first fatty acid reactant with the at least one second fatty acidreactant in the presence of the oligomerization catalyst to produce anestolide base oil.
 57. (canceled)
 58. The process according to claim 56,wherein the at least one first fatty acid reactant and the at least onesecond fatty acid reactant are continuously oligomerized in a reactor.59. The process according to claim 58, wherein the reactor is equippedwith a heat source.
 60. The process according to claim 58, wherein thereactor is a microwave reactor.
 61. The process according to claim 58,wherein the reactor is a continuous stirred tank reactor.
 62. Theprocess according to claim 56, wherein the oligomerizing produces one ormore first estolides. 63-67. (canceled)
 68. The process according toclaim 58, wherein the reactor is a column reactor.
 69. (canceled) 70.The process according to claim 68, wherein the reactor comprises a firstreaction stage.
 71. The process according to claim 70, wherein thereactor comprises two or more reaction stages.
 72. (canceled)
 73. Theprocess according to claim 71, wherein the oligomerization catalyst ispresent in one or more of the reaction stages. 74-81. (canceled)
 82. Theprocess according to claim 56, wherein the oligomerization catalystcomprises a Bronsted acid. 83-91. (canceled)
 92. The process accordingto claim 82, wherein the Bronsted acid is selected from at least one ofhydrochloric acid, nitric acid, sulfuric acid, phosphoric acid,perchloric acid, triflic acid, and p-TsOH.
 93. The process according toclaim 82, wherein the Bronsted acid is a solid-supported acid.
 94. Theprocess according to claim 82, wherein the Bronsted acid is selectedfrom acid-activated clays.
 95. The process according to claim 82,wherein the Bronsted acid is selected from acid-activatedmontmorillonite clays.
 96. The process according to claim 82, whereinthe Bronsted acid is selected from acidic mesoporous materials.
 97. Theprocess according to claim 82, wherein the Bronsted acid is selectedfrom zeolite materials.
 98. The process according to claim 59, whereinthe oligomerizing is carried out at a temperature that is greater than50° C.
 99. The process according to claim 98, wherein the oligomerizingis carried out at a temperature range of 50° C. to 100° C. 100-106.(canceled)
 107. The process according to claim 58, wherein the reactoris a plug flow reactor. 108-116. (canceled)